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

• -enantiomers with a ratio of 73:27, 4 is the pure (S)-enantiomer, and 5 is the (S)-enantiomer with 98% ee. The present study illustrates the diversity in the stereochemistry of anteiso branching in bacterial metabolites. Compounds 1−4 were moderately antimicrobial against Gram-positive bacteria and fungi, with

• MIC ranges of 6.25–25 μg/mL. Keywords: 1JC,H; alkanoylimidazoles; anteiso; Kocuria; nocarimidazole; Introduction The phylum Actinobacteria contains bacterial genera most prolific as producers of novel natural products with high structural diversity, unique modes of action, and potent bioactivities

• tetraoxide and sodium periodate in a biphasic solvent mixture (CCl4/MeCN/H2O), which gave 6-methyloctanoic acid (nat-10). The authentic (S)-6-methyloctanoic acid and (S)-8-methyldecanoic acid were synthesized in our previous studies [22][30]. These anteiso fatty acids were derivatized with a chiral

Isolation and biosynthesis of an unsaturated fatty acid with unusual methylation pattern from a coral-associated bacterium Microbulbifer sp.

• Amit Raj Sharma,
• Enjuro Harunari,
• Tao Zhou,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2019, 15, 2327–2332, doi:10.3762/bjoc.15.225

• anteiso position is the most common [19]. Branching at other positions is less common but represents a significant proportion of branched-chain fatty acids in some organisms [19]. Tuberculostearic acid (10-methyloctadecanoic acid (18:1 me(10)), 10- methylhexadecanoic acid (16:1 me(10)), and 10

N-Acylated amino acid methyl esters from marine Roseobacter group bacteria

• Hilke Bruns,
• Lisa Ziesche,
• Nargis Khakin Taniwal,
• Laura Wolter,
• Thorsten Brinkhoff,
• Jennifer Herrmann,
• Rolf Müller and
• Stefan Schulz

Beilstein J. Org. Chem. 2018, 14, 2964–2973, doi:10.3762/bjoc.14.276

• unsaturated NAMEs seems to be fixed at the ω-7 position [8][25]. Compound D (C19H37NO3) showed a mass spectrum identical to C15:0-NAME, albeit the retention index deviated by 38 units. A methyl branch at iso- or anteiso-position seemed likely. Therefore, the theoretical retention index Ic were calculated for

• retention index for iso-C15:0 and anteiso-C15:0-NAME are Ic = 2352 and Ic = 2365, respectively, while all other methyl branch locations had a lower value. The close similarity of Inat = 2354 and Ic = 2352 suggested the methyl branch to be located in the iso-position. Consequently, iso-C15:0-NAME (6) was

Volatile organic compounds produced by the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria 85-10

• Teresa Weise,
• Marco Kai,
• Anja Gummesson,
• Armin Troeger,
• Stephan von Reuß,
• Silvia Piepenborn,
• Francine Kosterka,
• Martin Sklorz,
• Ralf Zimmermann,
• Wittko Francke and
• Birgit Piechulla

Beilstein J. Org. Chem. 2012, 8, 579–596, doi:10.3762/bjoc.8.65

• compound and anteiso-branching for the later-eluting isomer [38][39][40]. In fact, mass spectra and retention times (co-injection) of 10-methylundecan-2-one (34) and 9-methylundecan-2-one (35) synthesized in our lab (Scheme 1) matched those of the respective natural products. Small amounts of the

• structures was largely facilitated: the unbranched ketones were found to be always accompanied by the iso-branched isomers and in some cases also by the anteiso-branched ones. Corresponding methylcarbinols could also be detected. The position of the double bond in a pentadecen-2-one (49), a member of the

• and one of 2-methylbutanol. Similarly, iso-leucine (its involvement in biosynthesis being supported by the presence of esters of 2-methylbutanol) will give rise to anteiso-branching. However, due to the general principles of chain elongation with acetate/malonate units, in X. c. pv. vesicatoria 85-10

Novel fatty acid methyl esters from the actinomycete Micromonospora aurantiaca

• Jeroen S. Dickschat,
• Hilke Bruns and
• Ramona Riclea

Beilstein J. Org. Chem. 2011, 7, 1697–1712, doi:10.3762/bjoc.7.200

• iso-branched starters isobutyryl-CoA (red) for iso-even FAs and isovaleryl-CoA (blue) for iso-odd FAs, whereas the same reactions from isoleucine yield (S)-2-methylbutyryl-CoA (green) for anteiso-odd FA biosynthesis. Internal methyl branches can be introduced through the use of methylmalonyl-CoA

• − 57]+ ion, which is typical for anteiso-FAMEs. The synthesis of methyl 8-methyldecanoate (95) as a reference compound was started from 1-bromo-2-methylbutane (117b, Scheme 3). Copper-catalysed 1,4-addition of the respective Grignard reagent to methyl acrylate in the presence of trimethylchlorosilane

• similar mass spectra, thus indicating a methyl group in a γ-position (Figure 5H shows the mass spectrum of methyl 4,8-dimethyldecanoate). The relatively high intensity of the [M − 57]+ fragment ion suggested the structures of anteiso-FAMEs, and accordingly, only the isoleucine-derived methyl esters of