Asymmetricreduction of methyl benzoylformate with the chiral NADHmodel 2 in the pyrido[3,2-c]azepin series afforded methyl mandelate in 91% optical yield. The high enantioselectivity observed with model 2 is compared with cyclized analogues 1a and 1b in the naphthyridine and pyrrolo[3,4-b]pyridine series respectively. The stereochimical outcome of the reaction is discussed in relation to the out-of-plane
Chiral NADH models with restricted or blocked rotation at the amide function: attempts to interpret the mechanism of the enantioselective hydrogen transfer to methyl benzoylformate
Various NADHmodels with the following characteristics were studied and compared with previously reported models: (1) use of (S)-phenylalaninol as chiral auxiliary; (2) orientation in or out of the plane of the amide carbonyl. Despite the occurrence of apparently similar characteristics, they gave very different results in the asymmetricreduction of methyl benzoylformate. A detailed NMR study was
The pyridinium reduction route to alkaloids: a synthesis of (±)-tashiromine
作者:Roderick W. Bates、Jutatip Boonsombat
DOI:10.1039/b100407g
日期:——
An indolizidine natural product, (±)-tashiromine, has been synthesized as a single diastereoisomer by a simple protocol. The key steps of the synthesis include a heterogeneous Sonogashira reaction and a stereoelectronically controlled reduction of a bicyclic pyridinium ion.