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Search for "monoterpene" in Full Text gives 42 result(s) in Beilstein Journal of Organic Chemistry.
One hundred years of benzotropone chemistry
- Arif Dastan,
- Haydar Kilic and
- Nurullah Saracoglu
Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98
- activity [14][15][16]. Troponoids 3–10 have been reported in the literature in a number of natural forms (Figure 1) [1][2][3][4][5][6][7][8]. These compounds have a structural class spacing from the simple monocyclic tropones, such as the potent antifungal and antibiotic monoterpene β-thujaplicin (4) [17
Graphical Abstract
Scheme 1: Tropone (1), tropolone (2) and their resonance structures.
Figure 1: Natural products containing a tropone nucleus.
Figure 2: Possible isomers 11–13 of benzotropone.
Scheme 2: Synthesis of benzotropones 11 and 12.
Scheme 3: Oxidation products of benzotropylium fluoroborate (16).
Scheme 4: Oxidation of 7-bromo-5H-benzo[7]annulene (22).
Scheme 5: Synthesis of 4,5-benzotropone (11) using o-phthalaldehyde (27).
Scheme 6: Synthesis of 4,5-benzotropone (11) starting from oxobenzonorbornadiene 31.
Scheme 7: Acid-catalyzed cleavage of oxo-bridge of 34.
Scheme 8: Synthesis of 4,5-benzotropone (11) from o-xylylene dibromide (38).
Scheme 9: Synthesis of 4,5-benzotropone (11) via the carbene adduct 41.
Scheme 10: Heck coupling strategy for the synthesis of 11.
Scheme 11: Synthesis of benzofulvalenes via carbonyl group of 4,5-benzotropone (11).
Figure 3: Some cycloheptatrienylium cations.
Scheme 12: Synthesis of condensation product 63 and its subsequent oxidative cyclization products.
Figure 4: A novel series of benzo[7]annulenes prepared from 4,5-benzotropone (11).
Scheme 13: Preparation of substituted benzo[7]annulene 72 using the Mukaiyama-Michael reaction.
Figure 5: Possible benzo[7]annulenylidenes 73–75.
Scheme 14: Thermal and photochemical decomposition of 7-diazo-7H-benzo[7]annulene (76) and the trapping of int...
Scheme 15: Synthesis of benzoheptafulvalene 86.
Scheme 16: Synthesis of 7-(diphenylmethylene)-7H-benzo[7]annulene (89).
Scheme 17: Reaction of 4,5-benzotropone (11) with dimethyl diazomethane.
Scheme 18: Synthesis of dihydrobenzomethoxyazocine 103.
Scheme 19: Synthesis and reducibility of benzo-homo-2-methoxyazocines.
Scheme 20: Synthesis of 4,5-benzohomotropones 104 and 115 from 4,5-benzotropones 11 and 113.
Scheme 21: A catalytic deuterogenation of 4,5-benzotropone (11) and synthesis of 5-monosubstituted benzo[7]ann...
Scheme 22: Synthesis of methyl benzo[7]annulenes 131 and 132.
Scheme 23: Ambident reactivity of halobenzo[7]annulenylium cations 133a/b.
Scheme 24: Preparation of benzo[7]annulenylidene–iron complexes 147.
Scheme 25: Synthesis of 1-ethynylbenzotropone (150) and the etheric compound 152 from 4,5-benzotropone (11) wi...
Scheme 26: Thermal decomposition of 4,5-benzotropone (11).
Scheme 27: Reaction of 4,5-benzotropone (11) with 1,2-ethanediol and 1,2-ethanedithiol.
Scheme 28: Conversions of 1-benzosuberone (162) to 2,3-benzotropone (12).
Scheme 29: Synthesis strategies for 2,3-bezotropone (12) using 1-benzosuberones.
Scheme 30: Oxidation-based synthesis of 2,3-benzotropone (12) via 1-benzosuberone (162).
Scheme 31: Synthesis of 2,3-benzotropone (12) from α-tetralone (171) via ring-expansion.
Scheme 32: Preparation of 2,3-benzotropone (12) by using of benzotropolone 174.
Figure 6: Benzoheptafulvenes as condensation products of 2,3-benzotropone (12).
Scheme 33: Conversion of 2,3-benzotropone (12) to tosylhydrazone salt 182 and gem-dichloride 187.
Figure 7: Benzohomoazocines 191–193 and benzoazocines 194–197.
Scheme 34: From 2,3-benzotropone (12) to carbonium ions 198–201.
Scheme 35: Cycloaddition reactions of 2,3-benzotropone (12).
Scheme 36: Reaction of 2,3-benzotropone (12) with various reagents and compounds.
Figure 8: 3,4-Benzotropone (13) and its resonance structure.
Scheme 37: Synthesis of 6,7-benzobicyclo[3.2.0]hepta-3,6-dien-2-one (230).
Figure 9: Photolysis and thermolysis products of 230.
Figure 10: Benzotropolones and their tautomeric structures.
Scheme 38: Synthesis strategies of 4,5-benzotropolone (238).
Scheme 39: Synthesis protocol for 2-hydroxy-4,5-benzotropone (238) using oxazole-benzo[7]annulene 247.
Figure 11: Some quinoxaline and pyrazine derivatives 254–256 prepared from 4,5-benzotropolone (238).
Scheme 40: Nitration product of 4,5-benzotropolone (238) and its isomerization to 1-nitro-naphthoic acid (259)....
Scheme 41: Synthesis protocol for 6-hydroxy-2,3-benzotropone (239) from benzosuberone (162).
Scheme 42: Various reactions via 6-hydroxy-2,3-benzotropone (239).
Scheme 43: Photoreaction of 6-hydroxy-2,3-benzotropone (239).
Scheme 44: Synthesis of 7-hydroxy-2,3-benzotropone (241) from benzosuberone (162).
Scheme 45: Synthesis strategy for 7-hydroxy-2,3-benzotropone (241) from ketone 276.
Scheme 46: Synthesis of 7-hydroxy-2,3-benzotropone (241) from β-naphthoquinone (280).
Scheme 47: Synthesis of 7-hydroxy-2,3-benzotropone (241) from bicyclic endoperoxide 213.
Scheme 48: Synthesis of 7-hydroxy-2,3-benzotropone (241) by ring-closing metathesis.
Figure 12: Various monosubstitution products 289–291 of 7-hydroxy-2,3-benzotropone (241).
Scheme 49: Reaction of 7-hydroxy-2,3-benzotropone (241) with various reagents.
Scheme 50: Synthesis of 4-hydroxy-2,3-benzotropones 174 and 304 from diketones 300/301.
Scheme 51: Catalytic hydrogenation of diketones 300 and 174.
Scheme 52: Synthesis of halo-benzotropones from alkoxy-naphthalenes 306, 307 and 310.
Figure 13: Unexpected byproducts 313–315 during synthesis of chlorobenzotropone 309.
Figure 14: Some halobenzotropones and their cycloadducts.
Scheme 53: Multisep synthesis of 2-chlorobenzotropone 309.
Scheme 54: A multistep synthesis of 2-bromo-benzotropone 26.
Scheme 55: A multistep synthesis of bromo-2,3-benzotropones 311 and 316.
Scheme 56: Oxidation reactions of 8-bromo-5H-benzo[7]annulene (329) with some oxidants.
Scheme 57: Synthesis of 2-bromo-4,5-benzotropone (26).
Scheme 58: Synthesis of 6-chloro-2,3-benzotropone (335) using LiCl and proposed intermediate 336.
Scheme 59: Reaction of 7-bromo-2,3-benzotropone (316) with methylamine.
Scheme 60: Reactions of bromo-2,3-benzotropones 26 and 311 with dimethylamine.
Scheme 61: Reactions of bromobenzotropones 311 and 26 with NaOMe.
Scheme 62: Reactions of bromobenzotropones 26 and 312 with t-BuOK in the presence of DPIBF.
Scheme 63: Cobalt-catalyzed reductive cross-couplings of 7-bromo-2,3-benzotropone (316) with cyclic α-bromo en...
Figure 15: Cycloadduct 357 and its di-π-methane rearrangement product 358.
Scheme 64: Catalytic hydrogenation of 2-chloro-4,5-benzotropone (311).
Scheme 65: Synthesis of dibromo-benzotropones from benzotropones.
Scheme 66: Bromination/dehydrobromination of benzosuberone (162).
Scheme 67: Some transformations of isomeric dibromo-benzotropones 261A/B.
Scheme 68: Transformations of benzotropolone 239B to halobenzotropolones 369–371.
Figure 16: Bromobenzotropolones 372–376 and 290 prepared via bromination/dehydrobromination strategy.
Scheme 69: Synthesis of some halobenzotropolones 289, 377 and 378.
Figure 17: Bromo-chloro-derivatives 379–381 prepared via chlorination.
Scheme 70: Synthesis of 7-iodo-3,4-benzotropolone (382).
Scheme 71: Hydrogenation of bromobenzotropolones 369 and 370.
Scheme 72: Debromination reactions of mono- and dibromides 290 and 375.
Figure 18: Nitratation and oxidation products of some halobenzotropolenes.
Scheme 73: Azo-coupling reactions of some halobenzotropolones 294, 375 and 378.
Figure 19: Four possible isomers of dibenzotropones 396–399.
Figure 20: Resonance structures of tribenzotropone (400).
Scheme 74: Two synthetic pathways for tribenzotropone (400).
Scheme 75: Synthesis of tribenzotropone (400) from dibenzotropone 399.
Scheme 76: Synthesis of tribenzotropone (400) from 9,10-phenanthraquinone (406).
Scheme 77: Synthesis of tribenzotropone (400) from trifluoromethyl-substituted arene 411.
Figure 21: Dibenzosuberone (414).
Figure 22: Reduction products 415 and 416 of tribenzotropone (400).
Figure 23: Structures of tribenzotropone dimethyl ketal 417 and 4-phenylfluorenone (412) and proposed intermed...
Figure 24: Structures of benzylidene- and methylene-9H-tribenzo[a,c,e][7]annulenes 419 and 420 and chiral phos...
Figure 25: Structures of tetracyclic alcohol 422, p-quinone methide 423 and cation 424.
Figure 26: Structures of host molecules 425–427.
Scheme 78: Synthesis of non-helical overcrowded derivatives syn/anti-431.
Figure 27: Hexabenzooctalene 432.
Figure 28: Structures of possible eight isomers 433–440 of naphthotropone.
Scheme 79: Synthesis of naphthotropone 437 starting from 1-phenylcycloheptene (441).
Scheme 80: Synthesis of 10-hydroxy-11H-cyclohepta[a]naphthalen-11-one (448) from diester 445.
Scheme 81: Synthesis of naphthotropone 433.
Scheme 82: Synthesis of naphthotropones 433 and 434 via cycloaddition reaction.
Scheme 83: Synthesis of naphthotropone 434 starting from 452.
Figure 29: Structures of tricarbonyl(tropone)irons 458, and possible cycloadducts 459.
Scheme 84: Synthesis of naphthotropone 436.
Scheme 85: Synthesis of precursor 465 for naphthotropone 435.
Scheme 86: Generation of naphthotropone 435 from 465.
Figure 30: Structures of tropylium cations 469 and 470.
Figure 31: Structures of tropylium ions 471+.BF4−, 472+.BF4−, and 473+.BF4−.
Scheme 87: Synthesis of tropylium ions 471+.BF4− and 479+.ClO4−.
Scheme 88: Synthesis of 1- and 2-methylanthracene (481 and 482) via carbene–carbene rearrangement.
Figure 32: Trapping products 488–490.
Scheme 89: Generation and chemistry of a naphthoannelated cycloheptatrienylidene-cycloheptatetraene intermedia...
Scheme 90: Proposed intermediates and reaction pathways for adduct 498.
Scheme 91: Exited-state intramolecular proton transfer of 505.
Figure 33: Benzoditropones 506 and 507.
Scheme 92: Synthesis of benzoditropone 506e.
Scheme 93: Synthetic approaches for dibenzotropone 507 via tropone (1).
Scheme 94: Formation mechanisms of benzoditropone 507 and 516 via 515.
Scheme 95: Synthesis of benzoditropones 525 and 526 from pyromellitic dianhydride (527).
Figure 34: Possible three benzocyclobutatropones 534–536.
Scheme 96: Synthesis of benzocyclobutatropones 534 and 539.
Scheme 97: Synthesis attempts for benzocyclobutatropone 545.
Scheme 98: Generation and trapping of symmetric benzocyclobutatropone 536.
Scheme 99: Synthesis of chloro-benzocyclobutatropone 552 and proposed mechanism of fluorenone derivatives.
Scheme 100: Synthesis of tropolone analogue 559.
Scheme 101: Synthesis of tropolones 561 and 562.
Figure 35: o/p-Tropoquinone rings (563 and 564) and benzotropoquinones (565–567).
Scheme 102: Synthesis of benzotropoquinone 566.
Scheme 103: Synthesis of benzotropoquinone 567 via a Diels–Alder reaction.
Figure 36: Products 575–577 through 1,2,3-benzotropoquinone hydrate 569.
Scheme 104: Structures 578–582 prepared from tropoquinone 567.
Figure 37: Two possible structures 583 and 584 for dibenzotropoquinone, and precursor compound 585 for 583.
Scheme 105: Synthesis of saddle-shaped ketone 592 using dibenzotropoquinone 584.
Iodine(III)-mediated halogenations of acyclic monoterpenoids
- Laure Peilleron,
- Tatyana D. Grayfer,
- Joëlle Dubois,
- Robert H. Dodd and
- Kevin Cariou
Beilstein J. Org. Chem. 2018, 14, 1103–1111, doi:10.3762/bjoc.14.96
- potential of the latter two vicinal difunctionalizations of terpenoids by not only expanding their substrate scope but also by trying to achieve other bromo-oxylations as well as analogous chloro- and/or iodofunctionalizations of linear terpenoids. For this purpose, five monoterpene derivatives – bearing
Graphical Abstract
Figure 1: Halogenated terpenoids from natural sources.
Scheme 1: Previously developed bromo-functionalizations of polyprenoids using iodine(III) reagents.
Figure 2: Selected monoterpenoids used in this study.
Scheme 2: Dibromination of acyclic monoterpenoids.
Scheme 3: Bromo(trifluoro)acetoxylation of acyclic monoterpenoids.
Scheme 4: Bromohydroxylation of acyclic monoterpenoids.
Scheme 5: Iodo(trifluoro)acetoxylation of acyclic monoterpenoids.
Scheme 6: Chlorination of acyclic monoterpenoids.
Scheme 7: General mechanism proposal for the formation of 2–6 and control experiments.
Pd(OAc)2/Ph3P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles
- Dominik Kellner,
- Maximilian Weger,
- Andrea Gini and
- Olga García Mancheño
Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175
- heterocyclic terpenes by subsequent (hetero)-Diels–Alder or [4 + 1]-cycloadditions with nitrenes is also depicted. Keywords: dimerization; heterocycles; isoprene; monoterpene; palladium catalysis; Introduction The dimerization of conjugated dienes represents a useful, highly atom economic and straightforward
- increase of the reactivity (86% yield), delivering the TT-linear terpene as the main product in a 16:1 ratio of 2-TT vs other dimeric isomers 2, along with Diels–Alder-generated cyclic monoterpene byproducts (Table 1, entry 4). Interestingly, the dimerization did not take place at temperatures below 90 °C
Graphical Abstract
Figure 1: Isoprene as chemical building block in nature and organic synthesis.
Scheme 1: Pd-catalyzed dimerization of isoprene.
Scheme 2: Putative mechanism for the Pd(OAc)2-catalyzed dimerization of isoprene.
Scheme 3: Functionalization of the isoprene-dimer 2-TT to substituted O- and N-heterocycles.
Diels–Alder reactions of myrcene using intensified continuous-flow reactors
- Christian H. Hornung,
- Miguel Á. Álvarez-Diéguez,
- Thomas M. Kohl and
- John Tsanaktsidis
Beilstein J. Org. Chem. 2017, 13, 120–126, doi:10.3762/bjoc.13.15
- applications, first and foremost in the fragrance and flavor industries, but also in the pharmaceutical and chemical industries [1][2][3]. Myrcene is a naturally occurring, acyclic monoterpene which is used industrially for the manufacture of flavoring substances and fragrances; in research it is used as a
Graphical Abstract
Scheme 1: Diels–Alder reaction of myrcene (1), with various dienophiles 2.
Figure 1: Kinetic studies of the Diels–Alder reaction between myrcene (1) and acrylic acid (2b); a) for diffe...
Figure 2: Comparison of conversions in three different reactors for the Diels–Alder reaction of myrcene (1) w...
A detailed view on 1,8-cineol biosynthesis by Streptomyces clavuligerus
- Jan Rinkel,
- Patrick Rabe,
- Laura zur Horst and
- Jeroen S. Dickschat
Beilstein J. Org. Chem. 2016, 12, 2317–2324, doi:10.3762/bjoc.12.225
- monooxygenases and acyl transferases [12][13]. Very few cases are known in which terpene cyclases generate an achiral product as exemplified by the monoterpene 1,8-cineol (eucalyptol, 1) and the sesquiterpenes germacrene B (2) and α-humulene (3) (Figure 1). A direct 1,6-cyclisation of the monoterpene precursor
- distinguished based on the labelling experiments described here. Discussion Plant and bacterial terpene cyclases show important structural differences [33]. While plant monoterpene synthases are composed of α and β domains and exhibit a quarternary α2β2 structure [34][35], bacterial mono- and sesquiterpene
Graphical Abstract
Figure 1: Selection of achiral terpenes.
Scheme 1: Cyclisation of GPP to 1 via the (R)-terpinyl cation ((R)-6, left) or the (S)-terpinyl cation ((S)-6...
Figure 2: Partial HSQC spectra showing the region of crosspeaks for HA and HB connected to C-3 and C-5 of A) ...
Figure 3: A) Partial HSQC spectrum showing the region of crosspeaks of C-2 with its directly connected hydrog...
Scheme 2: Mechanism for the cyclisation of FPP to corvol ethers A (19) and B (18). WMR: Wagner-Meerwein rearr...
The direct oxidative diene cyclization and related reactions in natural product synthesis
- Juliane Adrian,
- Leona J. Gross and
- Christian B. W. Stark
Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200
- considered in complement [4][5][6]. Oxidative cyclization – Historical background In 1924 Kötz and Steche reported on an investigation of the constitution of the monoterpene geraniol (1, R = H) [7]. Though the overall structure was known at that time, the position of one of the two C–C-double bonds within
Graphical Abstract
Scheme 1: Putative structures of geraniol 1a (R = H) or 1b (R = H) (in 1924), their expected dihydroxylation ...
Scheme 2: Correlation between the substrate double bond geometry and relative stereochemistry of the correspo...
Scheme 3: Mechanisms and classification for the metal-mediated oxidative cyclizations to form 2,5-disubstitut...
Scheme 4: Synthesis of (+)-anhydro-D-glucitol and (+)-D-chitaric acid using an OsO4-mediated oxidative cycliz...
Scheme 5: Total synthesis of neodysiherbaine A via a Ru(VIII)- and an Os(VI)-catalyzed oxidative cyclization,...
Scheme 6: Formal synthesis of ionomycin by Kocienski and co-workers.
Scheme 7: Total synthesis of amphidinolide F by Fürstner and co-workers.
Scheme 8: Brown`s and Donohoe`s oxidative cyclization approach to cis-solamin A.
Scheme 9: Total synthesis of cis-solamin A using a Ru(VIII)-catalyzed oxidative cyclization and enzymatic des...
Scheme 10: Donohoe´s double oxidative cyclization approach to cis-sylvaticin.
Scheme 11: Permanganate-mediated approach to cis-sylvaticin by Brown and co-workers.
Scheme 12: Total synthesis of membranacin using a KMnO4-mediated oxidative cyclization.
Scheme 13: Total synthesis of membrarollin and its analogue 21,22-diepi-membrarollin.
Scheme 14: Total synthesis of rollidecin C and D using a late stage Re(VII)-catalyzed oxidative polycyclizatio...
Scheme 15: Co(II)-catalyzed oxidative cyclization in the total synthesis of asimilobin and gigantetrocin A.
Scheme 16: Mn(VII)-catalyzed oxidative cyclization of a 1,5-diene in the synthesis of trans-(+)-linalool oxide....
Scheme 17: Re(VII)-catalyzed oxidative cyclization in the total synthesis of teurilene.
Scheme 18: Total synthesis of (+)-eurylene via Re(VII)- and Cr(VI)-mediated oxidative cyclizations.
Scheme 19: Synthesis of cis- and trans-THF Rings of eurylene via Mn(VII)-mediated oxidative cyclizations.
Scheme 20: Cr(VI)-catalyzed oxidative cyclization in the total synthesis of venustatriol by Corey et al.
Scheme 21: Ru(VIII)-catalyzed oxidative cyclization of a 1,5-diene in the synthesis and evaluation of its ster...
Scheme 22: Ru(VII)-catalyzed oxidative cyclization of a 5,6-dihydroxy alkene in the synthesis of the core stru...
Mechanistic investigations on six bacterial terpene cyclases
- Patrick Rabe,
- Thomas Schmitz and
- Jeroen S. Dickschat
Beilstein J. Org. Chem. 2016, 12, 1839–1850, doi:10.3762/bjoc.12.173
- interesting molecular properties. Particularly obvious is their often characteristic aroma that contributes to the typical flavour of many essential oils from plants. This is exemplified by the monoterpene α-pinene that occurs in form of both enantiomers in pine trees, while (R)-(+)-limonene is found in
- much later, with the first described compounds being geosmin [3] and 2-methylisoborneol [4], two irregular terpenoids that represent a degraded sesquiterpene [5] and a methylated monoterpene [6], respectively. These compounds have a musty or earthy aroma and are responsible for the smell of freshly
Graphical Abstract
Figure 1: Structures of sesquiterpenes obtained by incubation of FPP with bacterial sesquiterpene cyclases.
Figure 2: Contiguous spin systems observed by 1H,1H-COSY (bold), key HMBC and NOE correlations for a) α-amorp...
Figure 3: Contiguous spin systems observed by 1H,1H-COSY (bold), key HMBC and NOE correlations for a) 7-epi-α...
Scheme 1: Biosynthetic pathway from FPP to 7-epi-α-eudesmol (4).
Figure 4: Incubation experiments with (6-13C)FPP and the 7-epi-α-eudesmol synthase in deuterium oxide. a) 13C...
Figure 5: Incubation experiments with (13-13C)FPP. 13C NMR spectra of a) unlabelled 1 and (13-13C)-1, b) unla...
Selective bromochlorination of a homoallylic alcohol for the total synthesis of (−)-anverene
- Frederick J. Seidl and
- Noah Z. Burns
Beilstein J. Org. Chem. 2016, 12, 1361–1365, doi:10.3762/bjoc.12.129
- homoallylic alcohol. Critical factors for optimization of this reaction are highlighted. The utility of the product bromochloride is demonstrated by the first total synthesis of an antibacterial polyhalogenated monoterpene, (−)-anverene. Keywords: enantioselective catalysis; halogenation; natural products
Graphical Abstract
Scheme 1: Selective bromochlorination and possible disconnections for anverene (1).
Scheme 2: Selective total synthesis of (−)-anverene. Reagents and conditions: a) NBS (1.2 equiv), ClTi(OiPr)3...
Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate
- Sean P. Bew,
- Glyn D. Hiatt-Gipson,
- Graham P. Mills and
- Claire E. Reeves
Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103
- monoterpene nitrate (1R,2S)-(−)-myrtenol nitrate. Keywords: atmospheric chemistry; exchange reaction; halide; isoprene nitrate; monoterpene; Introduction Understanding the chemistry of the biosphere and its interaction with the atmosphere is fundamental to Earth System science. Such is the importance of
- monoterpenes account for a large percentage of the total emissions that are not non-methane VOCs. Furthermore although monoterpene emissions (127 Tg C yr−1) are significant lower than isoprene [6] (viz. 600 Tg C yr−1) they are nonetheless gaining in significance and are now considered to be important
- to monoterpene derived O-nitrate ester synthesis was undertaken using (1R,5S)-(−)-myrtenol (84) which was quickly and efficiently converted into the corresponding optically active 1° alkyl bromide 85 which, due to its instability, was used ‘as is’ [55]. Employing our standard silver nitrate
Graphical Abstract
Scheme 1: Simplified overview outlining how a small number of different IPNs are synthesised and are able to ...
Scheme 2: Protocols for the synthesis of O-nitrated alcohols using (±)-isoprene epoxide and 2° alcohols as st...
Scheme 3: Attempted synthesis of O-nitrate ester rac-19 and rac-20 synthesis.
Scheme 4: Olah et al. O-nitrated alcohol syntheses of 23–33 using N-nitro-2,4-6-trimethylpyridinium tetrafluo...
Scheme 5: O-nitration study using 22 and the alcohols 34–37.
Scheme 6: Silver nitrate mediated synthesis of 2-oxopropyl nitrate 43.
Scheme 7: Application of isoprene for the synthesis of precursors to IPNs and synthesis via ‘halide for nitra...
Scheme 8: Synthesis of (E)-3-methyl-4-chlorobut-2-en-1-ol ((E)-60) and (Z)-3-methyl-4-chlorobut-2-en-1-ol ((Z...
Scheme 9: Using NOESY interactions to establish the conformations of the C=C bonds within (E)-10 and (Z)-9.
Scheme 10: Synthesis of isoprene nitrates (E)-11 and (Z)-12 from ketone 63.
Scheme 11: Attempted synthesis of rac-8 from O-mesylate rac-71.
Scheme 12: Synthesis of O-nitrate 73 from O-mesylate 72.
Scheme 13: Attempted synthesis of 2° alcohol containing 1° nitrate ester rac-19 and the unexpected synthesis o...
Scheme 14: Synthesis of monoterpene derived (1R,5S)-(−)-myrtenol nitrate 86.
A practical way to synthesize chiral fluoro-containing polyhydro-2H-chromenes from monoterpenoids
- Oksana S. Mikhalchenko,
- Dina V. Korchagina,
- Konstantin P. Volcho and
- Nariman F. Salakhutdinov
Beilstein J. Org. Chem. 2016, 12, 648–653, doi:10.3762/bjoc.12.64
- -fluorohexahydro-2H-chromenes under the developed conditions, the reaction occurs with inversion of configuration. Keywords: chirality; fluorine; halo-Prins reaction; isopulegol; monoterpene; Introduction Recently, we have found that a reaction between para-mentha-6,8-dien-2,3-diol (1) and aromatic aldehydes in
Graphical Abstract
Scheme 1: Reaction between monoterpenoid 1 and aromatic aldehydes in the presence of K10 montmorillonite clay....
Scheme 2: The Prins reaction between homoallylic alcohols and aldehydes.
Scheme 3: Reaction of compound 1 with aldehyde 6f.
Scheme 4: A possible mechanism of the compound 2 and 8 formation.
Scheme 5: Reaction of isopulegol (4) with aldehyde 6a in the presence BF3·Et2O.
Thermal and oxidative stability of the Ocimum basilicum L. essential oil/β-cyclodextrin supramolecular system
- Daniel I. Hădărugă,
- Nicoleta G. Hădărugă,
- Corina I. Costescu,
- Ioan David and
- Alexandra T. Gruia
Beilstein J. Org. Chem. 2014, 10, 2809–2820, doi:10.3762/bjoc.10.298
- properties, and its antimicrobial [19] biological effects. Moreover, the anticancer potential of basil components has been studied [24]. These sensory and pharmaceutical properties of basil are primarily due to the presence of essential oil components, which consist of monoterpene hydrocarbons (e.g., β
- %) and methylchavicol (6) (19.6%), from oxygenated monoterpene and phenolic derivative compound classes, respectively. Limonene (1) was the most important component from the monoterpene class (0.5%), while other monoterpene derivatives in the O. basilicum L. essential oil were eucalyptol (2), camphor (5
Graphical Abstract
Figure 1: The main compounds identified in raw O. basilicum L. essential oils (a) and the degradation reactio...
Figure 2: The score plot from the PCA analysis of the O. basilicum L. essential oil compounds nanoencapsulati...
Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides
- Zsolt Szakonyi,
- Reijo Sillanpää and
- Ferenc Fülöp
Beilstein J. Org. Chem. 2014, 10, 2738–2742, doi:10.3762/bjoc.10.289
- addition was observed. Amino ester 11 was obtained as a single product and transformed to the corresponding amino acids 10A and 10D in good yields on the gram scale. Keywords: asymmetric synthesis; β-amino acid; chiral; Michael addition; monoterpene; Introduction In the past decade, cyclic β-amino acids
- ][34]. From this aspect, chiral, monoterpene-based α,β-unsaturated esters might be excellent starting materials, in which the natural monoterpene skeleton may serve as the chiral origin for the stereoselective construction of the β-amino acid moiety. Our present aim was the synthesis of new, limonene
Graphical Abstract
Scheme 1: Reagents and conditions: (i) 2-methyl-2-butene, t-BuOH, NaClO2 (aq), NaH2PO4 (aq), yield: 60%; (ii)...
Scheme 2: Reagents and conditions: (i) 2.4 equiv LiNBn2, dry THF, −78 °C, 6 h, then NH4Cl (aq), overall yield...
Figure 1: Structure of 10D and an ORTEP plot of its configuration.
Scheme 3: Reagents and conditions: (i) 2.4 equiv LiNBn2, dry THF, −78 °C, 6 h, then NH4Cl (aq), overall yield...
Scheme 4: Reagents and conditions: (i) 2.4 equiv lithium (R)-N-benzyl-N-α-methylbenzylamide, dry THF, −78 °C,...
Scheme 5: Reagents and conditions: (i) 0.2 equiv KOt-Bu/t-BuOH, 40 °C, 24 h, yield: 93% (7D), 91% (13); (ii) ...
Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules
- Thilo Focken and
- Stephen Hanessian
Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195
- inflammation and traumatic bleeding. The leaves and stems of this plant contain oleoside-type secoiridoid glucosides with structurally interesting tetrasubstituted cyclopentanoid monoterpene units [116]. Two representative examples of these glycosides are nudifloside A (151) and D (13), which share a common
Graphical Abstract
Figure 1: Examples of phosphonamide reagents used in stereoselective synthesis.
Figure 2: Natural products and bioactive molecules synthesized using phosphonamide-based chemistry (atoms, bo...
Scheme 1: Olefination with cyclic phosphonamide anions, mechanistic rationale, and selected examples 27a–d [18].
Scheme 2: Asymmetric olefination with chiral phosphonamide anions and selected examples 31a–d [1,22].
Scheme 3: Synthesis of α-substituted phosphonic acids 33a–e by asymmetric alkylation of chiral phosphonamide ...
Scheme 4: Asymmetric conjugate additions of C2-symmetric chiral phosphonamide anions to cyclic enones, lacton...
Scheme 5: Asymmetric conjugate additions of P-chiral phosphonamide anions generated from 40a and 44a to cycli...
Scheme 6: Asymmetric cyclopropanation with chiral chloroallyl phosphonamide 47, mechanistic rationale, and se...
Scheme 7: Asymmetric cyclopropanation with chiral chloromethyl phosphonamide 28d [59].
Scheme 8: Stereoselective synthesis of cis-aziridines 57 from chiral chloroallyl phosphonamide 47a [62].
Scheme 9: Synthesis of phosphonamides by (A) Arbuzov reaction, (B) condensation of diamines with phosphonic a...
Figure 3: Original and revised structure of polyoxin A (69) [24-26].
Scheme 10: Synthesis of (E)-polyoximic acid (9) [24-26].
Figure 4: Key assembly strategy of acetoxycrenulide (10) [41,42].
Scheme 11: Total synthesis of (+)-acetoxycrenulide (10) [41,42].
Scheme 12: Synthesis squalene synthase inhibitor 19 by asymmetric sulfuration (A) and asymmetric alkylation (B...
Figure 5: Key assembly strategy of fumonisin B2 (20) and its tricarballylic acid fragment 105 [45,46].
Scheme 13: Final steps of the total synthesis of fumonisin B2 (20) [45,46].
Figure 6: Selected examples of two subclasses of β-lactam antibiotics – carbapenems (111 and 112) and trinems...
Scheme 14: Synthesis of tricyclic β-lactam antibiotic 123 [97].
Scheme 15: Total synthesis of (−)-anthoplalone (8) [56].
Figure 7: Protein tyrosine phosphatase (PTP) inhibitors 130, 131 and model compounds 16, 132 and 133 [68].
Scheme 16: Synthesis of model PTP inhibitors 16a,b [68].
Scheme 17: Synthesis of aziridine hydroxamic acid 17 as MMP inhibitor [63].
Scheme 18: Synthesis of methyl jasmonate (11) [48].
Figure 8: Structures of nudiflosides A (137) and D (13) [49].
Scheme 19: Total synthesis of the pentasubstituted cyclopentane core 159 of nudiflosides A (151) and D (13) an...
Figure 9: L-glutamic acid (161) and constrained analogues [57,124].
Scheme 20: Stereoselective synthesis of DCG-IV (162) [57].
Scheme 21: Stereoselective synthesis of mGluR agonist 21 [124].
Figure 10: Key assembly strategy of berkelic acid (15) [43].
Scheme 22: Total synthesis of berkelic acid (15) [43].
Figure 11: Key assembly strategy of jerangolid A (22) and ambruticin S (14) [27,28].
Scheme 23: Final assembly steps in the total synthesis of jerangolid A [27].
Scheme 24: Key assembly steps in the total synthesis of ambruticin S (14) [28].
Figure 12: General steroid construction strategy based on conjugate addition of 212 to cyclopentenone 48, exem...
Scheme 25: Total synthesis of estrone (12) [44].
Selective allylic hydroxylation of acyclic terpenoids by CYP154E1 from Thermobifida fusca YX
- Anna M. Bogazkaya,
- Clemens J. von Bühler,
- Sebastian Kriening,
- Alexandrine Busch,
- Alexander Seifert,
- Jürgen Pleiss,
- Sabine Laschat and
- Vlada B. Urlacher
Beilstein J. Org. Chem. 2014, 10, 1347–1353, doi:10.3762/bjoc.10.137
- hydroxylation reactions leading to synthetically relevant intermediates [5][6][7][8][9][10][11]. In addition to chemical catalysts a range of enzymes has been studied for selective allylic hydroxylation of alkenes [12][13]. Among biosynthetic routes selective allylic hydroxylation of monoterpene olefines to
Graphical Abstract
Figure 1: Immediate heme surroundings shown for the nearest relative of CYP154E1 with available crystal struc...
Scheme 1: Terpene substrates (grey background) and their oxidised derivatives.
Scheme 2: a) Ac2O, pyridine, room temperature, 24 h; b) SeO2, t-BuOOH, CH2Cl2, 0 °C, 5 h; c) K2CO3, MeOH, roo...
Scheme 3: a) SeO2, t-BuOOH, CH2Cl2, 0 °C, 3.5 h.
Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics
- Gijs Koopmanschap,
- Eelco Ruijter and
- Romano V.A. Orru
Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50
- -3CR-approach with enantiopure monoterpene-based β-amino acids [43] (19, Scheme 8), giving 22 as major isomer [44]. The stereoselectivity for 22 was explained by the steric effects of the dimethyl bridge that might prefer a Re-attack of the isocyanide. Compared to methanol, again the reaction in water
Graphical Abstract
Scheme 1: The proposed mechanism of the Passerini reaction.
Scheme 2: The PADAM-strategy to α-hydroxy-β-amino amide derivatives 7. An additional oxidation provides α-ket...
Scheme 3: The general accepted Ugi-mechanism.
Scheme 4: Three commonly applied Ugi/cyclization approaches. a) UDC-process, b) UAC-sequence, c) UDAC-combina...
Scheme 5: Ugi reaction that involves the condensation of Armstrong’s convertible isocyanide.
Scheme 6: Mechanism of the U-4C-3CR towards bicyclic β-lactams.
Scheme 7: The Ugi 4C-3CR towards oxabicyclo β-lactams.
Scheme 8: Ugi MCR between an enantiopure monoterpene based β-amino acid, aldehyde and isocyanide resulting in...
Scheme 9: General MCR for β-lactams in water.
Scheme 10: a) Ugi reaction for β-lactam-linked peptidomimetics. b) Varying the β-amino acid resulted in β-lact...
Scheme 11: Ugi-4CR followed by a Pd-catalyzed Sn2 cyclization.
Scheme 12: Ugi-3CR of dipeptide mimics from 2-substituted pyrrolines.
Scheme 13: Joullié–Ugi reaction towards 2,5-disubstituted pyrrolidines.
Scheme 14: Further elaboration of the Ugi-scaffold towards bicyclic systems.
Scheme 15: Dihydroxyproline derivatives from an Ugi reaction.
Scheme 16: Diastereoselective Ugi reaction described by Banfi and co-workers.
Scheme 17: Similar Ugi reaction as in Scheme 16 but with different acids and two chiral isocyanides.
Scheme 18: Highly diastereoselective synthesis of pyrrolidine-dipeptoids via a MAO-N/MCR-procedure.
Scheme 19: MAO-N/MCR-approach towards the hepatitis C drug telaprevir.
Scheme 20: Enantioselective MAO-U-3CR procedure starting from chiral pyrroline 64.
Scheme 21: Synthesis of γ-lactams via an UDC-sequence.
Scheme 22: Utilizing bifunctional groups to provide bicyclic γ-lactam-ketopiperazines.
Scheme 23: The Ugi reaction provided both γ- as δ-lactams depending on which inputs were used.
Scheme 24: The sequential Ugi/RCM with olefinic substrates provided bicyclic lactams.
Scheme 25: a) The structural and dipole similarities of the triazole unit with the amide bond. b) The copper-c...
Scheme 26: The Ugi/Click sequence provided triazole based peptidomimetics.
Scheme 27: The Ugi/Click reaction as described by Nanajdenko.
Scheme 28: The Ugi/Click-approach by Pramitha and Bahulayan.
Scheme 29: The Ugi/Click-combination by Niu et al.
Scheme 30: Triazole linked peptidomimetics obtained from two separate MCRs and a sequential Click reaction.
Scheme 31: Copper-free synthesis of triazoles via two MCRs in one-pot.
Scheme 32: The sequential Ugi/Paal–Knorr reaction to afford pyrazoles.
Scheme 33: An intramolecular Paal–Knorr condensation provided under basic conditions pyrazolones.
Scheme 34: Similar cyclization performed under acidic conditions provided pyrazolones without the trifluoroace...
Scheme 35: The Ugi-4CR towards 2,4-disubstituted thiazoles.
Scheme 36: Solid phase approach towards thiazoles.
Scheme 37: Reaction mechanism of formation of thiazole peptidomimetics containing an additional β-lactam moiet...
Scheme 38: The synthesis of the trisubstituted thiazoles could be either performed via an Ugi reaction with pr...
Scheme 39: Performing the Ugi reaction with DMB-protected isocyanide gave access to either oxazoles or thiazol...
Scheme 40: Ugi/cyclization-approach towards 2,5-disubstituted thiazoles. The Ugi reaction was performed with d...
Scheme 41: Further derivatization of the thiazole scaffold.
Scheme 42: Three-step procedure towards the natural product bacillamide C.
Scheme 43: Ugi-4CR to oxazoles reported by Zhu and co-workers.
Scheme 44: Ugi-based synthesis of oxazole-containing peptidomimetics.
Scheme 45: TMNS3 based Ugi reaction for peptidomimics containing a tetrazole.
Scheme 46: Catalytic cycle of the enantioselective Passerini reaction towards tetrazole-based peptidomimetics.
Scheme 47: Tetrazole-based peptidomimetics via an Ugi reaction and a subsequent sigmatropic rearrangement.
Scheme 48: Resin-bound Ugi-approach towards tetrazole-based peptidomimetics.
Scheme 49: Ugi/cyclization approach towards γ/δ/ε-lactam tetrazoles.
Scheme 50: Ugi-3CR to pipecolic acid-based peptidomimetics.
Scheme 51: Staudinger–Aza-Wittig/Ugi-approach towards pipecolic acid peptidomimetics.
Figure 1: The three structural isomers of diketopiperazines. The 2,5-DKP isomer is most common.
Scheme 52: UDC-approach to obtain 2,5-DKPs, either using Armstrong’s isocyanide or via ethylglyoxalate.
Scheme 53: a) Ugi reaction in water gave either 2,5-DKP structures or spiro compounds. b) The Ugi reaction in ...
Scheme 54: Solid-phase approach towards diketopiperazines.
Scheme 55: UDAC-approach towards DKPs.
Scheme 56: The intermediate amide is activated as leaving group by acid and microwave assisted organic synthes...
Scheme 57: UDC-procedure towards active oxytocin inhibitors.
Scheme 58: An improved stereoselective MCR-approach towards the oxytocin inhibitor.
Scheme 59: The less common Ugi reaction towards DKPs, involving a Sn2-substitution.
Figure 2: Spatial similarities between a natural β-turn conformation and a DKP based β-turn mimetic [158].
Scheme 60: Ugi-based syntheses of bicyclic DKPs. The amine component is derived from a coupling between (R)-N-...
Scheme 61: Ugi-based synthesis of β-turn and γ-turn mimetics.
Figure 3: Isocyanide substituted 3,4-dihydropyridin-2-ones, dihydropyridines and the Freidinger lactams. Bio-...
Scheme 62: The mechanism of the 4-CR towards 3,4-dihydropyridine-2-ones 212.
Scheme 63: a) Multiple MCR-approach to provide DHP-peptidomimetic in two-steps. b) A one-pot 6-CR providing th...
Scheme 64: The MCR–alkylation–MCR procedure to obtain either tetrapeptoids or depsipeptides.
Scheme 65: U-3CR/cyclization employing semicarbazone as imine component gave triazine based peptidomimetics.
Scheme 66: 4CR towards triazinane-diones.
Scheme 67: The MCR–alkylation–IMCR-sequence described by our group towards triazinane dione-based peptidomimet...
Scheme 68: Ugi-4CR approaches followed by a cyclization to thiomorpholin-ones (a) and pyrrolidines (b).
Scheme 69: UDC-approach for benzodiazepinones.
Scheme 70: Ugi/Mitsunobu sequence to BDPs.
Scheme 71: A UDAC-approach to BDPs with convertible isocyanides. The corresponding amide is cleaved by microwa...
Scheme 72: microwave assisted post condensation Ugi reaction.
Scheme 73: Benzodiazepinones synthesized via the post-condensation Ugi/ Staudinger–Aza-Wittig cyclization.
Scheme 74: Two Ugi/cyclization approaches utilizing chiral carboxylic acids. Reaction (a) provided the product...
Scheme 75: The mechanism of the Gewald-3CR includes three base-catalysed steps involving first a Knoevnagel–Co...
Scheme 76: Two structural 1,4-thienodiazepine-2,5-dione isomers by U-4CR/cyclization.
Scheme 77: Tetrazole-based diazepinones by UDC-procedure.
Scheme 78: Tetrazole-based BDPs via a sequential Ugi/hydrolysis/coupling.
Scheme 79: MCR synthesis of three different tricyclic BPDs.
Scheme 80: Two similar approaches both involving an Ugi reaction and a Mitsunobu cyclization.
Scheme 81: Mitsunobu–Ugi-approach towards dihydro-1,4-benzoxazepines.
Scheme 82: Ugi reaction towards hetero-aryl fused 5-oxo-1,4-oxazepines.
Scheme 83: a) Ugi/RCM-approach towards nine-membered peptidomimetics b) Sequential peptide-coupling, deprotect...
Scheme 84: Ugi-based synthesis towards cyclic RGD-pentapeptides.
Scheme 85: Ugi/MCR-approach towards 12–15 membered macrocycles.
Scheme 86: Stereoselective Ugi/RCM approach towards 16-membered macrocycles.
Scheme 87: Passerini/RCM-sequence to 22-membered macrocycles.
Scheme 88: UDAC-approach towards 12–18-membered depsipeptides.
Figure 4: Enopeptin A with its more active derivative ADEP-4.
Scheme 89: a) The Joullié–Ugi-approach towards ADEP-4 derivatives b) Ugi-approach for the α,α-dimethylated der...
Scheme 90: Ugi–Click-strategy for 15-membered macrocyclic glyco-peptidomimetics.
Scheme 91: Ugi/Click combinations provided macrocycles containing both a triazole and an oxazole moiety.
Scheme 92: a) A solution-phase procedure towards macrocycles. b) Alternative solid-phase synthesis as was repo...
Scheme 93: Ugi/cyclization towards cyclophane based macrocycles.
Scheme 94: PADAM-strategy towards eurystatin A.
Scheme 95: PADAM-approach for cyclotheanamide.
Scheme 96: A triple MCR-approach affording RGD-pentapeptoids.
Scheme 97: Ugi-MiBs-approach towards peptoid macrocycles.
Scheme 98: Passerini-based MiB approaches towards macrocycles 345 and 346.
Scheme 99: Macrocyclic peptide formation by the use of amphoteric aziridine-based aldehydes.
A new intermediate in the Prins reaction
- Shinichi Yamabe,
- Takeshi Fukuda and
- Shoko Yamazaki
Beilstein J. Org. Chem. 2013, 9, 476–485, doi:10.3762/bjoc.9.51
- produced when pinene (a bicyclic monoterpene) was heated with paraformaldehyde. However, Prins performed the first rather comprehensive study of the reactions between formaldehyde and hydrocarbons with C=C double bonds [2][3]. These were styrene, pinene, camphene and anethole. As a catalyst, sulfuric acid
Graphical Abstract
Scheme 1: A general scheme of the Prins reaction.
Scheme 2: An example of the Prins reaction [4]. The product yields (%) are based on formaldehyde.
Scheme 3: An equilibrium in the hydrolysis of the product, 1,3-dioxane.
Scheme 4: Formation of the acetate of an allylic alcohol by Prins reaction [5].
Scheme 5: A reaction mechanism involving the carbonium-ion intermediate X.
Scheme 6: A reaction model composed of RHC=CH2, (H2C=O)2 and H3O+(H2O)13 to obtain the path of step 2 (Scheme 5). H3O+...
Figure 1: Geometries of the precursor and the transition states (TSs) of the Prins reaction of propene with (...
Figure 2: Energy changes (in kcal/mol) of the propene Prins reaction calculated by B3LYP/6-311+G(d,p) SCRF=(P...
Figure 3: Geometries of the transition states (TSs) of the Prins reaction of styrene + (formaldehyde)2 + H3O+...
Figure 4: Energy changes (in kcal/mol) of the styrene Prins reaction calculated by B3LYP/6-311+G(d,p) SCRF = ...
Figure 5: TS1(Ph) geometries of n = 20 and n = 30 in the reacting system of styrene + H3O+(H2O)n + (H2C=O)2 c...
Scheme 7: Summary of the present calculated results. The ether in the box is the new intermediate found in th...
Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones
- Nicole Zimmermann,
- Robert Hilgraf,
- Lutz Lehmann,
- Daniel Ibarra and
- Wittko Francke
Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140
- analysis (GC/CIMS) showed the molecular mass of the compound to be M+ = 168, while high resolution mass spectrometry (GC/HRMS) proved its atomic composition to be C10H16O2, suggesting an oxygenated monoterpene as the target structure. The fragmentation pattern, exhibited in the 70 eV EI-mass spectrum
Graphical Abstract
Figure 1: Terpenoids 1–5 present in Alloxysta victrix and cis-fused bicyclic iridoids known from other insect...
Figure 2: 70 eV EI-mass spectrum of the iridoid X, a component of the volatile secretions of the parasitoid w...
Figure 3: Structures and gas chromatographic retention times of trans-fused dihydronepetalactones on a conven...
Scheme 1: Route from (S)-pulegone to the mixture of dihydronepetalactones a and b, consequently following Wol...
Figure 4: Configuration of the dihydronepetalactone a.
Figure 5: Route to stereochemically pure trans-fused dihydronepetalactones a–d from (R)-limonene.
Scheme 2: Synthesis of the key compound 16. Reaction conditions: a) O3, MeOH, −50 °C (86%); b) AcOH, piperidi...
Scheme 3: Synthesis of trans,trans-substituted dihydronepetalactone b. Reaction conditions: a) TBDMSCl, imida...
Figure 6: Configurations of compound 24 and the dihydronepetalactone b.
Scheme 4: Synthesis of cis,trans-substituted dihydronepetalactone c. Reaction conditions: a) Crabtree's catal...
Figure 7: Configurations of compound 26 and the dihydronepetalactone c.
Scheme 5: Synthesis of a 2:3 mixture of dihydronepetalactones c and d. Reaction conditions: a) (COCl)2, DMSO,...
Scheme 6: Formal synthesis of a mixture of dihydronepetalactones a and b from (R)-limonene.
