Chemical investigation of secondary metabolites from a marine-derived actinomycete strain of the genus Kocuria, isolated from a stony coral Mycedium sp., led to the identification of two new alkanoylimidazoles, nocarimidazoles C (1) and D (2) as well as three known congeners, nocarimidazoles A (3) and B (4) and bulbimidazole A (5). Structure analysis of 1 and 2 by NMR and MS revealed that both are 4-alkanoyl-5-aminoimidazoles with a 6-methyloctanoyl or decanoyl chain, respectively. Two possible positions of the amino group on the imidazole rings (C-2 and C-5) posed a challenge in the structure study, which was settled by the measurement of ¹J_C,H coupling constants for comparison with those of synthetically prepared model imidazoles. The absolute configurations of the anteisoalkanoyl group present in 1, 4, and 5 were determined by low-temperature HPLC analysis of the degradation products labeled with a chiral anthracene reagent, which revealed that 1 is a mixture of the R- and S-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.

中文翻译：

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Nocarimidazoles C和D，来自珊瑚的放线菌Kocuria sp。的抗菌烷氨基咪唑：1JC，H偶联常数在确定微生物代谢物中取代咪唑的确定性和前异烷基链立体化学多样性中的应用

从该属的海洋来源的放线菌菌株的次级代谢产物的化学调查Kocuria，从石珊瑚分离Mycedium属，导致了两个新alkanoylimidazoles的鉴定，nocarimidazoles C（1）和d（2），以及三个已知同类物，诺卡咪唑A（3）和B（4）和灯泡咪唑A（5）。1和2的结构分析NMR和MS分析表明，它们都是分别具有6-甲基辛酰基或癸酰基链的4-烷酰基-5-氨基咪唑。咪唑环上两个氨基的可能位置（C-2和C-5）对结构研究提出了挑战，该问题通过测量¹ J _C，H偶联常数与合成模型比较来解决。咪唑。本anteisoalkanoyl组中的绝对构型1，4和5分别由标与手性蒽试剂，其显示该降解产物的低温HPLC分析测定1是的混合物[R -和小号-比例为73:27的对映体，其中4是纯的（S）对映体，5是具有98％ee的（S）对映体。本研究说明了细菌代谢产物中前异分支的立体化学的多样性。化合物1 - 4是对革兰氏阳性菌和真菌的抗微生物适度，与MIC范围6.25-25微克/毫升的。