cyclopentadiene gave the mixture of adducts 3a-d. Major diastereoisomer, the (1S,exo)-adduct (3a), was isolated in 57% yield and transformed in 74% overall yield into (+)-(1S)-N-benzoyl-2-azabicyclo-[2.2.1]heptan-3-one (8), which was compared with an authentic sample of its enantiomer. In the course of this transformation sequence, the chiral auxiliary (1R)-8-phenylmenthol was recovered in 90% yield.
(1R)-8-苯基薄荷基
乙醛酸的N-苄基
亚胺的Diels-Alder环加成反应得到
环戊二烯,得到加合物3a-d的混合物。以57%的收率分离出主要的非对映异构体((1 S,exo)-加合物(3a),以74%的总收率转化为(+)-(1 S)-N-苯甲酰基-
2-氮杂双环-[2.2]。 1]庚3-3-酮(8),与其对映异构体的真实样品进行比较。在该转化过程中,以90%的收率回收了手性辅助(1R)-
8-苯基薄荷醇。