Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• between the diastereomer pairs. The enantiomer ratio of 4 was estimated to be S/R = 56:44 or near by chiral phase HPLC analysis of 4' on a cellulose tribenzoate-coated silica gel column (Figure 4). Thus, 4 was concluded to be an enantiomeric mixture of (2E,4E)-7-hydroxy-2,4-dimethyl-2,4-octadienoic acid

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

Highly stereocontrolled total synthesis of racemic codonopsinol B through isoxazolidine-4,5-diol vinylation

• Lukáš Ďurina,
• Anna Ďurinová,
• František Trejtnar,
• Ľuboš Janotka,
• Lucia Messingerová,
• Jana Doháňošová,
• Ján Moncol and
• Róbert Fischer

Beilstein J. Org. Chem. 2021, 17, 2781–2786, doi:10.3762/bjoc.17.188

• at 4.22 ppm referred to the 2,3-syn configuration. Whereas the above mentioned addition was highly diastereoselective, the same reaction under identical conditions but in the absence of CeCl3 resulted in the formation of a small amount of the anti,anti diastereomer of 4 (anti,syn/anti,anti, 80:20

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• % (R)-CPA 2, the benzyl-substituted 3-alkenylindole 81 (dienophile) was subjected to a Povarov cycloaddition with the commonly used imine 80, giving the 2,3,4-tetrahydroquinoline as a single diastereomer in high yield and enantioselectivity and finely tolerating the high steric requirements necessary

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• hydroxyoxathiolane 32. Further, acetylation of the hydroxyoxathiolane in the presence of methanesulfonic acid gave a 1:2 mixture of the trans-diastereomer 33 and the cis-diastereomer 34. The esterification using ʟ-menthol as a chiral auxiliary resulted in a diastereomeric mixture, which was successfully

• ). The other diastereomer 59 remained dissolved in the mother liquor. The treatment of the norephedrine salt 58 with 5 M HCl afforded the enantiopure acid 60, which was further converted to the desired 1,3-oxathiolane-substituted ʟ-menthyl ester 35a. The synthetic use of [1,2]-Brook rearrangement for the

• a cis/trans ratio of 1.3:1 for the nucleoside intermediate 79a. Further, the nucleoside intermediate 79a was deprotected using a type of basic resin. This gave the cis-diastereomer 3TC (1), which was purified by chiral HPLC, resulting in an ee value of 70% (Scheme 28). Further developments in the

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• ratio of 86:14 and high enantiomeric purity of 95:5 er for the major diastereomer (Table 1, entry 1). Using chloroform/isopropyl alcohol 9:1 as the solvent mixture afforded after 120 hours, aldehyde 10a in 45% yield with 83:17 dr and 97:3 er (Table 1, entry 2). The Michael addition in methanol catalyzed

• nitroalkene. The nitroalkene is in synclinal orientation with respect to the enamine double bond. The alternative si-attack on the nitroalkene provides the minor diastereomer (S,R)-10. The enantiomeric products (R,R)- and (R,S)-10 could be formed via the Michael addition from the si-face of the enamine. In

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• influence the stereo-outcome for the later cyclopropanation step. Thus, treatment of 25 with diethylzinc and diiodomethane delivered the expected syn-cyclopropyl carbinol 26 as the major diastereomer (dr 95:5) in 90% yield. After the protection of the secondary alcohol as MOM ether, the primary alcohol was

• vinylmagnesium bromide. The allylic alcohol products 71 and 72 were obtained as a diastereomeric mixture in 86% yield with poor stereoselectivity. To gain more of the desired diastereomer 71, the mixture of 71 and 72 was subjected to a two-step procedure involving a Dess–Martin oxidation followed by

• expected syn adduct in 65% yield as a single diastereomer. Oxidation of this molecule under Swern conditions proceeded smoothly giving ketone 91 in 94% yield, which was highlighted as an important observation as the same transformation using the similar compound was reported to be unsuccessful [14]. Ring

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• of 28-2, which was accompanied by 45% of unreacted 28-1. Interestingly, pure (R)-isomer 28-1 was obtained in 20% yield from the unreacted 28-1. The diastereomer separation of 28-2 was achieved by column chromatography to separate the (R)- and (S)-isomers of 28-2 in 21 and 31% yields, respectively

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

•  23A) afforded trans-decalin 54 as the major diastereomer [83]. In the second case, a radical addition/aldolization was successfully developed to afford another trans-decalin unity as a major diastereomer in a 10:1 diasteroisomeric ratio (Scheme 23B, 57) [84]. Notably, in both cases, four contiguous

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• mixture of starting material 6, the conjugate addition product 14, and a trace of the denitration product 15. The structure of both compounds was confirmed by single X-ray crystallography (Figure 4 and Figure 5). The addition of methanol is stereoselective with only a single diastereomer of 14 being

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• addition of the chiral auxiliary. Our attention then turned to the stereoselective reduction of 8. Chelation-controlled reduction of 8 using ZnCl2 and DIBALH allowed for the successful formation of 16 as a single diastereomer (Scheme 4), as evidenced by 1H NMR spectroscopy [18]. TBS deprotection furnished

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• water (50 mL), dried over Na2SO4, and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel (hexane/EtOAc 1:1) to give the alcohol [6.90 g, 16.7 mmol, 83%, Rf = 0.45 (hexane/EtOAc 1:1)] as a single diastereomer; yellow solid; mp 102.5–104.0 °C; IR (ATR

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• Lewis acid, which furnished the expected tetrahydropyran 23 as a single diastereomer via an oxocarbenium intermediate 21 (Scheme 5) [29][30]. The reaction was dependent from the nature of the aromatic ring, which plays a crucial role in the product formation. Homoallylic alcohols with an electron-rich

• ]. A strategy involving BiCl3-catalyzed microwave-assisted Prins cyclization of homoallylic alcohol 101 with an aldehyde 102 was successfully employed for the synthesis of 4-chloro-cis-2,6-disubstituted tetrahydropyran 103 as a single diastereomer [57], as shown in Scheme 23. In continuation, 4

• and homoallylic alcohol 110 using TMSCl and NaI. Furthermore, the major diastereomer was utilized for the synthesis of centrolobine, as shown in Scheme 26 [60]. Loh and co-workers have shown the construction of cis-2,6-disubstituted tetrahydropyran 116 with an exocyclic double bond by reacting

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• the inhibition of viral miRNA through carbon dot-mediated delivery [144]. A diastereomer of LNA, α-ʟ-LNA (Figure 7B), also induces a higher affinity for both DNA and RNA complements in addition to providing a high stability against nucleases [145][146]. Unlike LNA, this diastereomer is a mimic of DNA

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• enantiomer to diastereomer. A plausible mechanism is shown in Scheme 19. In the presence of acid, EDA complex 52 is formed by ketene 48 and diamine 51. Then, the ground state 52 transforms into excited state 53 or into unproductive charge-transfer excited state 54 that can restore ground state 52 by BET

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• oxide ((R)-7b) provided the product (2S,4R)-9i in a much better 8:1 anti/syn coupling diastereoselectivity (Table 2, entry 10). The configuration of the major anti-diastereomer of alkoxyamine 9j was determined by X-ray crystallography after desilylation and hydrochloride formation (see Supporting

• furnished the dioxygenated amide 9l with a 7:1 anti/syn diastereoselectivity for the radical coupling (Table 2, entry 13). When the reaction was quenched after completion of the Brook rearrangement, N-allyl-N-propyl-2-(2-((trimethylsilyl)oxy)cyclohexyl)acetamide was obtained as a single diastereomer because

• substituent at the nitrogen atom also plays essentially no role for the diastereoselectivity of the cyclization (Table 3, entry 10 vs entry 9). The minor cis-diastereomer of N-(1-β-naphthylethyl)pyrrolidone 12j crystallized after oxidation to ketone 13j and its configuration was unequivocally established by X

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

Au(III) complexes with tetradentate-cyclam-based ligands

• Ann Christin Reiersølmoen,
• Thomas N. Solvi and
• Anne Fiksdahl

Beilstein J. Org. Chem. 2021, 17, 186–192, doi:10.3762/bjoc.17.18

• [51], which showed that JohnPhos-Au(I) and pyr-menthol-Au(III) complexes provided high amounts of the initially formed cis diastereomer in this model reaction. In contrast, some BOX-Au(III) complexes have the additional ability to rapidly transform the initially formed cis product into the isomerized

Direct synthesis of anomeric tetrazolyl iminosugars from sugar-derived lactams

• Michał M. Więcław and
• Bartłomiej Furman

Beilstein J. Org. Chem. 2021, 17, 115–123, doi:10.3762/bjoc.17.12

• of products As presented in Table 2, only one diastereomer of the desired iminosugar is obtained in almost all cases. This outstanding selectivity has been observed before and is described in our previous works devoted to the functionalization of sugar-derived lactams [23][24][25]. We explain it in

• between protons H2 and H7, suggest that it may be the diastereomer 2-(R), as shown in Figure 3. This result would be in accordance with the previously mentioned Woerpel’s model. The structure of compound 5b was assigned per analogiam, as diagnostic signals in 1H NMR spectrum were also overlapped. We made

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• Lee [24] independently in 2003. (Scheme 1C and Scheme 1D) In Krische’s synthesis, a stereospecific intramolecular phosphine-catalyzed [3 + 2] cycloaddition of 2-butynoate with electron-deficient alkene 29 afforded cycloadduct 31 in 88% yield as a single diastereomer [25] (Scheme 1C). Later, Lee`s

• and co-workers disclosed the palladium-catalyzed intermolecular carboxylative TMM [3 + 2] cycloaddition [36] (Scheme 3). Exposure of coumarin 61 to the silyl-substituted TMM precursor 62 in the presence of a catalytic amount of Pd(PPh3)4 afforded adduct 63 in 81% yield as a single diastereomer (Scheme

• the desired alcohol 133 in 75% yield as a single diastereomer. Allylic oxidation of freshly prepared 133 with SeO2 followed by silylation with TBSOTf/Et3N afforded enyne 134. Enyne 134 was subjected to rhodium-catalyzed intramolecular [3 + 2] cycloaddition with a catalytic amount of [Rh(cod)OH]2 to

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

• Viola Kolaříková,
• Markéta Rybáčková,
• Martin Svoboda and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2020, 16, 2757–2768, doi:10.3762/bjoc.16.226

• (13, 108 mg, 0.624 mmol) were dissolved in CH2Cl2 (4 mL) and the mixture was stirred for 130 h at rt. After evaporation, the mixture was purified by gradient column chromatography (eluent hexane/EtOAc 2.5:1 → 2.4:1) to give the major diastereomer (probably endo-trans-14B, 50 mg, 25%, white solid, Rf

• = 0.17 for hexane/EtOAc 2.5:1) and the minor diastereomer (probably exo-cis-14C, 28 mg, 14%, clear solid, Rf = 0.24 for hexane/EtOAc 2.5:1). A mixture of the two diastereomers (14 mg, 7%, 14B/14C 2:1) and starting N-phenylmaleimide (58 mg, 54%) were also recovered. Major diastereoisomer (probably endo

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Lipophilicity trends upon fluorination of isopropyl, cyclopropyl and 3-oxetanyl groups

• Benjamin Jeffries,
• Zhong Wang,
• Robert I. Troup,
• Anaïs Goupille,
• Jean-Yves Le Questel,
• Charlene Fallan,
• James S. Scott,
• Elisabetta Chiarparin,
• Jérôme Graton and
• Bruno Linclau

Beilstein J. Org. Chem. 2020, 16, 2141–2150, doi:10.3762/bjoc.16.182

• , which was explained by the facially polar motif caused by the C–F dipoles present on the same side of the ring. Consequently, the diastereomer B4 possessed a higher lipophilicity, although the lipophilicity of the vicinally difluorinated diastereomers B3 and B5 was identical, and also the same as the

Convenient access to pyrrolidin-3-ylphosphonic acids and tetrahydro-2H-pyran-3-ylphosphonates with multiple contiguous stereocenters from nonracemic adducts of a Ni(II)-catalyzed Michael reaction

• Alexander N. Reznikov,
• Dmitry S. Nikerov,
• Anastasiya E. Sibiryakova,
• Victor B. Rybakov,
• Evgeniy V. Golovin and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2020, 16, 2073–2079, doi:10.3762/bjoc.16.174

• formed (Table 1, entries 6 and 7). After this, the reaction was carried out in an aqueous–organic medium. Fortunately, an individual diastereomer of Henry/acetalyzation product 13a was obtained when K2CO3 in combination with TEBAC was used as a catalyst. A THF/water ratio of 7.5:1 is important in order