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

• 1995, was previously identified as a polyamine with C2 symmetry and a 1,3-syn-diol moiety on a C10 carbon backbone – one of very few substituted polyamines to be isolated from nature. Its absolute configuration was later established by our first reported total synthesis in 2010. Herein we report the

Analogs of the carotane antibiotic fulvoferruginin from submerged cultures of a Thai Marasmius sp.

• Birthe Sandargo,
• Leon Kaysan,
• Rémy B. Teponno,
• Christian Richter,
• Benjarong Thongbai,
• Frank Surup and
• Marc Stadler

Beilstein J. Org. Chem. 2021, 17, 1385–1391, doi:10.3762/bjoc.17.97

• of potential pharmaceutical interest. Klein et al. obtained a crystal structure of fulvoferruginin (1) [8], as did Huneck et al. for hercynolactone [9], verifying their relative configuration. Huo et al. have further confirmed the absolute configuration of compound 1 by utilizing the CD exciton

• biosynthetic genes as the parent compound, and postulate that the congeners should also have the same absolute configuration as compound 1 [10]. For a long time, fulvoferruginin was only known to be produced by a strain of M. fulvoferrugineus found in Northern America, but there is a recent report on the

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

• diastereoselectivities were observed with less bulky methyl 2-bromo-2-butenoate (R2 = CH3CH=), leading to an almost complete loss of cis/trans selectivity by the reaction with aliphatic aldimines 14. The absolute configuration of the reaction products was unambiguously determined after X-ray crystallographic analysis of

• reaction of N-tert-butanesulfinyl trifluoromethyl ketimines (SS)-37 with dimethylsulfoxonium methylide 38 gave trifluoromethylated aziridines 39 in moderate to excellent yields (45–93%), and good diastereoselectivities (86:14 to >99:1 dr). The absolute configuration of compounds 39 was determined by X-ray

Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• 9 ring system (Scheme 1). The absolute configuration of compound 9 was determined by 2D NMR spectroscopic techniques. Clear NOE signals were observed between the H-7a and Me-10 as well as the Ha-9 and Me-10 protons. Beside NOESY experiments, the structure was also elucidated by X-ray crystallography

• configuration depicted in Scheme 2. Beside 2D NMR spectroscopic studies, the absolute configuration of compound 12 was determined by its transformation into the corresponding aminodiols 13 and 14, comparing the products with those obtained from the regioisomer 9 (discussed in Scheme 3). Synthesis and

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• product was ultimately obtained at room temperature (83% ee, Table 2, entry 3). The absolute configuration of the product was assigned as “S” by comparing the obtained optical rotation value with the values in the literature for the organocatalytic SMA of thiols to trans-chalcone derivatives [29][42]. A

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

• Wilfred J. M. Lewis,
• David M. Shaw and
• Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

• ) the jenamidines A–C, from another Streptomyces sp. strain [12], although these molecules were not recognized as pyrrolizidines until Snider’s subsequent synthetic work revised the structural assignment [13][14] and, separately, established the absolute configuration of natural (+)-NP25302 [15

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• value reported by the group of R. J. K. Taylor. Therefore, the absolute configuration assignment of (3R)-inthomycin C ((–)-3) as described by the Ryu and Hatakeyama groups contradicted with that of the R. J. K. Taylor group. Later, the groups of Hale and Hatakeyama tried hard to eliminate all the

Chemical constituents of Chaenomeles sinensis twigs and their biological activity

• Joon Min Cha,
• Dong Hyun Kim,
• Lalita Subedi,
• Zahra Khan,
• Sang Un Choi,
• Sun Yeou Kim and
• Chung Sub Kim

Beilstein J. Org. Chem. 2020, 16, 3078–3085, doi:10.3762/bjoc.16.257

• Supporting Information File 1). The strong NOESY cross-peaks of H-2 with H-6 and H-11 and H-6 with H-11 indicated that these three protons are co-facial (Figure 2B and Supporting Information File 1). The absolute configuration of C-6 was assigned as S by a well-established ECD empirical rule [22]. In brief

• and the analysis of the ΔδS-R values of all protons in 1a indicated a 2S and 9R configuration (Figure 2D). Finally, the absolute configuration of the glucopyranose was assigned as ᴅ by comparing the retention time of its chiral derivative with those of authentic samples [16][26]. Therefore, the

• , a systemic analysis of the ECD data of 13 with its diastereomers and simple derivatives showed that a positive or negative Cotton effect around 240–245 nm is indicative of the 6R or 6S configuration, respectively. From a positive Cotton effect at 245 nm of compound 1 (Figure 2C, left), the absolute

3-Acetoxy-fatty acid isoprenyl esters from androconia of the ithomiine butterfly Ithomia salapia

• Florian Mann,
• Daiane Szczerbowski,
• Lisa de Silva,
• Melanie McClure,
• Marianne Elias and
• Stefan Schulz

Beilstein J. Org. Chem. 2020, 16, 2776–2787, doi:10.3762/bjoc.16.228

• , microderivatizations, and synthesis of representative compounds. The absolute configuration of 12 was determined to be R. The two subspecies differed not only in the composition of the ester bouquet, but also in the composition of more volatile androconial constituents. While some individuals of I. s. aquinia

• -enoate (12) was performed to verify the structural proposal and to determine the absolute configuration of the natural product (Scheme 4). The commercially available epoxide (S)-22 served as chiral starting material. 1,9-Nonanediol (19) was monobrominated and oxidized with IBX to yield 9-bromononanal (20

• eluting ester is isoprenyl (Z)-3-acetoxy-13-octadecenoate, while the earlier eluting one is the 11-isomer. With optically active material in hand, the absolute configuration of 12 was determined by enantioselective gas chromatography. Because direct separation of the large esters seemed to be difficult

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• (Figure S31, Supporting Information File 1). Thus, the amino substitution at C-5 in 1 was unequivocally established (Figure 3). The absolute configuration at C-11 in the anteisoalkanoyl chain was determined by the Ohrui–Akasaka method [29]. The imidazole ring was degraded by oxidation using ruthenium

• (chromatographically equivalent to (R)-10-(R)-2A1P) and 184 min for (S)-10-(R)-2A1P, and nat-10-(R)-2A1P gave both peaks with the area ratio of 72.9:27.1 (Figure 4a). Therefore, 1 was confirmed as an enantiomeric mixture comprising 73% of the R- and 27% of the S-enantiomer. We also analyzed the absolute configuration

• of nocarimidazole B (4) produced by strain TK35-5. The same compound was originally isolated from marine Nocadiopsis, but the absolute configuration was not elucidated. The conversion of 4 into the derivative nat-11-(R)-2A1P, followed by HPLC analysis, revealed that 4 is an enantiomerically pure S

Asymmetric Mannich reactions of (S)-N-tert-butylsulfinyl-3,3,3-trifluoroacetaldimines with yne nucleophiles

• Ziyi Li,
• Li Wang,
• Yunqi Huang,
• Haibo Mei,
• Hiroyuki Konno,
• Hiroki Moriwaki,
• Vadim A. Soloshonok and
• Jianlin Han

Beilstein J. Org. Chem. 2020, 16, 2671–2678, doi:10.3762/bjoc.16.217

• synthesis of chiral α-trifluoromethylated propargylamines. In order to determine the absolute configuration of the chiral addition products, we successfully performed a crystallographic analysis of the minor product 3a. The structure is shown in Figure 2, the absolute configuration of the newly generated

Computational tools for drawing, building and displaying carbohydrates: a visual guide

• Kanhaya Lal,
• Rafael Bermeo and
• Serge Perez

Beilstein J. Org. Chem. 2020, 16, 2448–2468, doi:10.3762/bjoc.16.199

• of completion, the full description of a monosaccharide should obey the following rules: absolute configuration>[]. It is thus necessary to include such information

Muyocopronones A and B: azaphilones from the endophytic fungus Muyocopron laterale

• Ken-ichi Nakashima,
• Junko Tomida,
• Tomoe Tsuboi,
• Yoshiaki Kawamura and
• Makoto Inoue

Beilstein J. Org. Chem. 2020, 16, 2100–2107, doi:10.3762/bjoc.16.177

• ′/H-3′ (J = 8.2 Hz) and H-3′/H-4′ (J = 3.2 Hz). To establish the absolute configuration of the side chain, we therefore employed the modified Mosher’s method [21]. Although we initially attempted the preparation of the α-methoxy-α-trifluoromethylphenylacetic acid (MTPA) esters using 1.2 equivalents of

• shifts between 1a and 1b (Δδ(S)-MTPA−(R)-MTPA), the absolute configuration of the side chain was established to be the (2′R,3′R,4′S) configuration (Scheme 1B). The absolute configuration at the C-7 position of the azaphilones can be established by the positive and negative Cotton effects at the longest

• wavelength around 360 nm corresponding to 7S and 7R [22][23][24]. Therefore, positive Cotton effects at 325 and 355 nm in the electronic circular dichroism (ECD) spectrum of 1 indicated that the absolute configuration of the C-7 position was S (Figure 3). Furthermore, the coupling constant between H-10/H-11

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

• (Scheme 2). An X-ray diffraction study [50] of the formyl derivative 10a showed its (2R,3R,4S)-configuration (Figure 3). The absolute configuration of the other phosphonates 10b–d and 11b–d is assumed by analogy. Hydrogenation of phosphonates 6d,f with o-anisyl and bulky adamantan-1-yl substituents at the

Controlling the stereochemistry in 2-oxo-aldehyde-derived Ugi adducts through the cinchona alkaloid-promoted electrophilic fluorination

• Yuqing Wang,
• Gaigai Wang,
• Anatoly A. Peshkov,
• Ruwei Yao,
• Muhammad Hasan,
• Manzoor Zaman,
• Chao Liu,
• Stepan Kashtanov,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2020, 16, 1963–1973, doi:10.3762/bjoc.16.163

• favored by the parent alkaloids featuring free alcohol moiety (e.g., Q-Bn favored the formation of the enantiomer of 12 with the absolute configuration opposite to the one favored by Q). Substrates 8h and 8i were tested with only four cinchona alkaloid derivatives, but the observed stereochemical trends

• appeared to be consistent with those established for the rest of arylamine-derived Ugi adducts 8d–g. Finally, we attempted to determine the absolute configuration of a stereocenter for the major enantiomer of the representative fluorinated product. Using a sample of product 12e with the ee value of 74% we

Synthesis of monophosphorylated lipid A precursors using 2-naphthylmethyl ether as a protecting group

• Jundi Xue,
• Ziyi Han,
• Gen Li,
• Khalisha A. Emmanuel,
• Cynthia L. McManus,
• Qiang Sui,
• Dongmian Ge,
• Qi Gao and
• Li Cai

Beilstein J. Org. Chem. 2020, 16, 1955–1962, doi:10.3762/bjoc.16.162

• )-3-hydroxytetradecanoate (5) in 98% yield. The same hydrogenation reaction was carried out using the (S)-Ru(OAc)2(BINAP) catalyst. Then both the R and S products were compared using chiral HPLC to confirm the absolute configuration and enantiomeric purity (Figure S1, Supporting Information File 1

Three new O-isocrotonyl-3-hydroxybutyric acid congeners produced by a sea anemone-derived marine bacterium of the genus Vibrio

• Dandan Li,
• Enjuro Harunari,
• Tao Zhou,
• Naoya Oku and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1869–1874, doi:10.3762/bjoc.16.154

• describe the isolation, structure elucidation, including the absolute configuration, and bioactivity of 1–4. Results and Discussion The producing strain was cultured in a sea water-based medium and then extracted with n-BuOH. The extract was successively fractionated by silica gel chromatography using a

• , respectively (Figure 1). A database search identified the planar structure of 4 in a patent that described 5 (Figure 1) from marine obligate Vibrio sp. C-984 [9]. To determine the absolute configuration of C3 in 1–4, an anisotropy-based chiral analysis using a chiral derivatization reagent, phenylglycine

Nonenzymatic synthesis of anomerically pure, mannosyl-based molecular probes for scramblase identification studies

• Giovanni Picca,
• Markus Probst,
• Simon M. Langenegger,
• Oleg Khorev,
• Peter Bütikofer,
• Anant K. Menon and
• Robert Häner

Beilstein J. Org. Chem. 2020, 16, 1732–1739, doi:10.3762/bjoc.16.145

• configuration at the anomeric position and to prove the working principle of our synthetic strategy, we used 2D NMR experiments. Coupled HSQC measurements revealed the 1JCH coupling constants of our compounds and thereby the absolute configuration at the anomeric center of the carbohydrate [40][41][42]. For MPC

NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

• Alyn T. Davies,
• Mark D. Greenhalgh,
• Alexandra M. Z. Slawin and
• Andrew D. Smith

Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

• tolerated, giving a consistent diastereoselectivity of ≈75:25 dr (Scheme 2). Following chromatographic purification, the desired products 12–14, respectively, were isolated in 59–71% yield as single diastereoisomers with excellent enantioselectivity (95:5 to >99:1 er). The relative and absolute

• configuration of (2S,3S)-β-trifluoromethyl-β-hydroxyamide 12 was confirmed by single crystal X-ray crystallographic analysis, with all other products in this series assigned by analogy to 12 [57]. The introduction of an electron-donating p-tolyl substituent was also tolerated in the system, providing the

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• absolute configuration of the Trp residue was determined using a chiral derivatizing reagent, phenylglycine methyl ester (PGME) [21]. Compound 1 was reacted with both enantiomers of PGME to give (R)- and (S)-PGME amides 5a and 5b, and the difference of the 1H NMR chemical shifts ΔδS−R was calculated around

• effects at 236 nm and 217 nm, respectively, which was consistent with a Cotton effect pattern predicted for the Sa-atropisomer of 1b. Moreover, the overall spectral feature of the experimental and calculated ECDs were quite similar with each other (Figure 5). Based on these results, the absolute

• configuration of 1 was concluded to be 2S,2'S,2''S,6Sa. Pseudosporamicin A (2) was obtained as white amorphous solid. An HRESITOFMS analysis gave a deprotonated molecular ion [M − H]− at m/z 831.5255, which corresponded to the molecular formula having 10 degrees of unsaturation, C47H76O12. The 1H and 13C NMR

Efficient synthesis of dipeptide analogues of α-fluorinated β-aminophosphonates

• Marcin Kaźmierczak and
• Henryk Koroniak

Beilstein J. Org. Chem. 2020, 16, 756–762, doi:10.3762/bjoc.16.69

• Herein, we present an efficient synthesis of dipeptide analogues of α-fluorinated β-aminophosphonates. Each step of the synthesis was optimized to provide excellent yields. Moreover, the absolute configuration of the obtained compounds was determined by X-ray analysis, which proved the stereochemistry

• regioselectivity of the fluorination reaction. The absolute configuration of the obtained compounds was determined and confirmed by X-ray analysis. Furthermore, we present the use of α-fluorinated β-aminophosphonates as building blocks in the synthesis of their dipeptide analogues. In addition, we show the results

• ]. Crystallization of derivative 14c from D2O brought the expected results. The analysis confirmed the structure of the resulting compound 14c. The absolute configuration of 14c is consistent with the stereochemistry we proposed based on NMR studies. The crystals of 14c contained the (1R,2S)-diastereoisomer (Figure

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

•  11). This innovative methodology allowed the installation of the vicinal exo‐methylene branches characteristic for the cytotoxic marine natural product amphidinolide V as well as the determination of its absolute configuration. It further enabled the synthesis of a set of diastereomers and analogs of

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• enantioselectivities. Aliphatic chains gave a high degree of enantioselectivity (up to 98%), while more moderate ees were noted when the substrates were branched at the γ-site (Scheme 70) [133]. The absolute configuration at each stereogenic center was determined by subsequent conversion of the borylated acylimidazole

Asymmetric synthesis of CF₂-functionalized aziridines by combined strong Brønsted acid catalysis

• Xing-Fa Tan,
• Fa-Guang Zhang and
• Jun-An Ma

Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60

• dr values, including alkyl or halogen-substituted phenyl and 2-naphthyl ketones (Scheme 2). Unfortunately, phenylglyoxal monohydrates bearing strong electron-withdrawing groups were not compatible with the current conditions. X-ray analysis of aziridine 4a confirmed the absolute configuration of the