Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

• Daisuke Hirose and
• Tsuyoshi Taniguchi

Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196

• the mutifunctionalized product 19 as a single isomer. The stereochemistry of 19 could be presumably assigned by considering the 1,5-hydrogen shift mechanism (entry 5) [17]. The reaction of alkene 10 bearing a methyl ester moiety gave γ-lactone 20 by intramolecular transesterification with a tertiary

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• were separated on a silica-gel column. After the treatment of benzyl bromide in the presence of NaH, the acidic work-up delivered two diastereoisomers of lactone 17 (Route A). This was further confirmed by an alternative synthesis based on a known procedure [56], in which 3-substituted-γ-lactone 17 was

• derived from the stereoselective alkylation of Bn-protected 5-hydroxymethyl-γ-lactone 16 (Route B). Two diastereoisomers of the trans-isomer of 17 (ratio 4/1) were identical with compounds from the PIFA-promoted cyclization (Scheme 6, Route A). Based on these conclusive experiments, we believe that the 5

• -hydroxymethyl-γ-lactone, which has been widely found in natural products and compounds of pharmaceutical interest [65][66][67][68]. The usual methods including the alkylation at C-3 or the iodolactonization of amides or esters comprises multiple production steps, such as the hydrolysis of the halogen compounds

A new approach toward the total synthesis of (+)-batzellaside B

• Jolanta Wierzejska,
• Shin-ichi Motogoe,
• Yuto Makino,
• Tetsuya Sengoku,
• Masaki Takahashi and
• Hidemi Yoda

Beilstein J. Org. Chem. 2012, 8, 1831–1838, doi:10.3762/bjoc.8.210

• chromatography and then derivatized to trans-1,2-dibenzyloxy-substituted γ-lactone, which allows a precise assignment of the absolute configuration by comparison with the specific optical rotation value [34]. Accordingly, the primary hydroxy group of 12a-B was chemoselectively protected as the TBS ether [35] and

• upon treatment with NaIO4 [36] followed by PCC oxidation to form the corresponding trans-1,2-dibenzyloxy-substituted γ-lactone 14B in 17% yield over six steps. For comparison, optical rotation measurement was performed on a solution of 14B in CHCl3 at c 0.36. Indeed, this compound exhibited optical

• activity with an [α]D24 value of −51.6, indicative of an opposite sense of absolute configuration in comparison to the literature data given for (1S,2S)-dibenzyloxy γ-lactone ([α]D25 +60.1, c 1.0, CHCl3) [34]. From this, we can conclude, as seen in Scheme 2, that the more polar triol 12a-A obtained as a

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• precursors 17a and 17b in excellent yields (84% and 87%, respectively). Cycloaddition precursors 17a and 17b showed a much lower reactivity in the cycloadditions in comparison to the amides 13. For ester 17a, after microwave irradiation at 160 °C for 2 h, the desired cycloadduct 17a with the annulated γ

• -lactone was produced in good yield (80%). In contrast, 17b, with the longer tether (n = 2) failed to produce the desired δ-lactone under any conditions. A sharp decrease in reactivity in intramolecular IEDDA reactions of alkynes tethered to 1,2,4-triazines upon progression from 5- to 6-membered ring

Conserved and species-specific oxylipin pathways in the wound-activated chemical defense of the noninvasive red alga Gracilaria chilensis and the invasive Gracilaria vermiculophylla

• Martin Rempt,
• Florian Weinberger,
• Katharina Grosser and
• Georg Pohnert

Beilstein J. Org. Chem. 2012, 8, 283–289, doi:10.3762/bjoc.8.30

• oxylipins. Common products are 7,8-dihydroxyeicosatetraenoic acid and a novel eicosanoid with an unusual γ-lactone moiety. Several prostaglandins were predominantly formed by the invasive species. The role of some of these metabolites was investigated by surveying the attachment of E. peruviana on

• assigned, but the stereochemistry of the double bond C7/C8 remained open. The signal at 5.0 ppm in the proton range (proton at C4) and the resonance at 80.45 ppm (13C, HMBC, C4) as well as HMBC and 1H–1H COSY signals led to the assignment of a γ-lactone ring (Scheme 1). HMBC correlations from the carbon C4

Efficient oxidation of oleanolic acid derivatives using magnesium bis(monoperoxyphthalate) hexahydrate (MMPP): A convenient 2-step procedure towards 12-oxo-28-carboxylic acid derivatives

• Jorge A. R. Salvador,
• Vânia M. Moreira,
• Rui M. A. Pinto,
• Ana S. Leal and
• José A. Paixão

Beilstein J. Org. Chem. 2012, 8, 164–169, doi:10.3762/bjoc.8.17

• , anti-inflammatory, hepatoprotective, gastroprotective, antimicrobial, antidiabetic, and hemolytic properties, as well as many others [3][4][5]. Functionalized γ-lactones are important building blocks of bioactive natural products [6][7]. The δ-hydroxy-γ-lactone motif is part of such bioactive natural

• triterpenoids bearing a γ-lactone function, either isolated from natural sources or obtained by semisynthesis, have shown interesting biological activities [12][13][14]. From the synthetic point of view, the oxidative 28,13β-lactonization allows the preparation of 12α-hydroxyoleananes with a protected 28

• equiv of MMPP, in refluxing acetonitrile, afforded the corresponding δ-hydroxy-γ-lactone 2 in 85% yield after 5 hours (Table 1, entry 1). These new reaction conditions were successfully extended to OA 3 and other 3β-substituted OA derivatives 5, 7 and 9 (Table 1, entries 2–5). The substrates were

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• demonstrated that homobimetallic ruthenium–indenylidene complex 1 is a suitable catalyst precursor for the tandem RCM/ATRC of polyhalogenated α,ω-dienes 4 and 8 into the corresponding bicyclic γ-lactam derivatives. A more complex cascade sequence involving RCM and ATRA reactions afforded γ-lactone 18 starting

Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride

• Subrata Kumar Chaudhuri,
• Manabendra Saha,
• Amit Saha and
• Sanjay Bhar

Beilstein J. Org. Chem. 2010, 6, 748–755, doi:10.3762/bjoc.6.94

• chemoselective reduction of the oxo-group, occasionally with subsequent transesterification and the formation of the alkoxy-modified β-hydroxyesters. γ-Oxoesters react chemoselectively with sodium borohydride to produce the corresponding γ-hydroxyesters [1][2][17][23][24][25][26][27] (sometimes in the form of γ

• -lactone) [24]. Following the above noted literature precedences [1][2][17][22][23][24][25][26][27] on the utility of NaBH4, we attempted to reduce 4-aryl-4-oxoesters with methanolic NaBH4 chemoselectively. Surprisingly, we found that 4-aryl-4-oxoesters underwent facile reduction of both the keto and the

Synthesis of phosphonate and phostone analogues of ribose-1-phosphates

• Pitak Nasomjai,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2009, 5, No. 37, doi:10.3762/bjoc.5.37

• enzyme which converts 5 to 6 during the biosynthesis. Results and Discussion The target phosphonates 8 and 9 have been prepared by routes A and B as shown in Scheme 1 and Scheme 2 respectively. The routes start either from D-ribonic-γ-lactone (12) or D-ribose (13). For each route the key synthetic steps

• are the same involving installation of the dimethyl phosphonate moiety on a 2,3-O-isopropylidene ribofuranoside via a Wadsworth-Emmons reaction [4]. Route A (Scheme 2) started with acetonide protection of D-ribonic-γ-lactone (12) to generate 2,3-isopropylidene 14 [5]. Fluorination of the free 5

• -hydroxyl group with Deoxo-fluor™ [6] gave 5-deoxy-5-fluoro-2,3-O-isopropylidene-D-ribonic-γ-lactone (15) in good yield and then subsequent reduction of lactone 15 with NaBH4 resulted in the fully reduced diol 16. Diol 16 has been previously synthesised [7], however this route appears to offer a more

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• . These include mono-tetrahydrofurans, adjacent bis-tetrahydrofurans, nonadjacent bis-tetrahydrofurans, tri-tetrahydrofurans, adjacent tetrahydrofuran-tetrahydropyrans, nonadjacent tetrahydrofuran-tetrahydropyrans, mono-tetrahydropyrans, and acetogenins containing only γ-lactone. This review emphasizes

• identified from the roots of Uvaria acuminata, more than 400 members of this family of compounds have been isolated from 51 different species [7]. The common skeleton is most often characterised by an unbranched C32 or C34 fatty acid ending in a γ-lactone. Several oxygenated functions, such as hydroxyls

• synthesized by Wu’s group in 1999 [30] which used a palladium-catalyzed cross-coupling reaction between the butenolide 39 and the THF unit 22 as the key step for constructing the backbone of 36 (Scheme 5). The synthesis of aldehyde 37 began with D-xylose and involved construction of a γ-lactone moiety

Phase- vanishing halolactonization of neat substrates

• Nicole Windmon and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2008, 4, No. 29, doi:10.3762/bjoc.4.29

• iodine failed, while iodolactonization of the corresponding disodium salt gave a mixture of γ- and δ-lactones [16]. However, no experimental details were given. Under phase-vanishing conditions, treatment of 14 with iodine gave the corresponding γ-lactone 16 in a moderate yield. The yield was inferior

Photosonochemical catalytic ring opening of α-epoxyketones

• Hamid R. Memarian and
• Ali Saffar-Teluri

Beilstein J. Org. Chem. 2007, 3, No. 2, doi:10.1186/1860-5397-3-2

• the corresponding γ-lactone. [19] In our recent study, we have used 1-benzyl-2,4,6-triphenylpyridinium tetrafluoroborate (NBTPT) as photocatalyst in a highly diastereoselective ring opening of α-epoxyketones in acetone solution with the formation of 1.3-dioxolanes. [20] Ring opening of epoxides and α

Stereoselective α-fluoroamide and α-fluoro- γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

• Kenny Tenza,
• Julian S. Northen,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2005, 1, No. 13, doi:10.1186/1860-5397-1-13

• -actives of pharmaceutical interest.[15] It is well known too that selective fluorination can improve pharmacokinetics and the fluorine substituent can often modify bio-activity in an advantageous manner.[16] For example in the structural series relevant to this study the α-fluorinated-γ-lactone 5 is a key