Williams R M, Sanz-Cervera J F, Sancenón F, Marco J A, Halligan K M
Department of Chemistry, Colorado State University, Fort Collins 80523, USA.
Bioorg Med Chem. 1998 Aug;6(8):1233-41. doi: 10.1016/s0968-0896(98)00102-3.
A potentially bio-mimetic Diels-Alder cyclization to construct the bicyclo[2.2.2] ring system common to the paraherquamides, marcfortines, sclerotamides, brevianamides, VM55599, and asperparaline is reported. Epi-deoxybrevianamide E (22) is converted into the corresponding lactim ether (23) and then oxidized with DDQ to provide an azadiene (24) which is tautomerized in the presence of base to azadiene 25 which, spontaneously cyclizes to give a 2:1 mixture of cycloadducts 26 and 27. These cycloadducts are each in turn, converted into D,L-C-19-epi-brevianamide A (20) and D,L-brevianamide B (6). The stereochemical implications of the [4 + 2] cycloaddition is discussed in the context of a working hypothesis on the biosynthesis of this family, particularly VM55599.
报道了一种潜在的仿生狄尔斯-阿尔德环化反应，用于构建对映海葵酰胺、麦角福汀、硬皮酰胺、短杆菌酰胺、VM55599和曲霉帕拉林中共有的双环[2.2.2]环系。表脱氧短杆菌酰胺E（22）转化为相应的内酰胺醚（23），然后用DDQ氧化得到氮杂二烯（24），其在碱存在下互变异构为氮杂二烯25，后者自发环化生成环加成物26和27的2:1混合物。这些环加成物依次分别转化为D，L-C-19-表短杆菌酰胺A（20）和D，L-短杆菌酰胺B（6）。在关于该家族生物合成的工作假设的背景下，特别是VM55599，讨论了[4 + 2]环加成的立体化学意义。
