Reductive decarboxylation of bicyclic prolinic systems: a new approach to the enantioselective synthesis of the Geissman-Waiss lactone. X-ray structure determination of a key lactone intermediate

Journal of the Brazilian Chemical Society

Ambrósio, João Carlos L.¹  Universidade Estadual de Campinas, Campinas, Brazil¹  Santos, Regina Helena de A.¹  Universidade de São Paulo, São Carlos, Brazil¹  Correia, Carlos R. D.¹ 

关键词: Geissman-Waiss lactone;    [2+2]cycloadditions;    decarboxylation;    pyrrolizidine alkaloids;   

DOI  :  10.1590/S0103-50532003000100006

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

Two concise and enantioselective syntheses of the necine base precursors (1R,5R)-N-Cbz and N-Boc-2-oxa-6-azabicyclo[3.3.0]octan-3-ones (Geissman-Waiss lactones) were carried out from two enantiomerically pure endocyclic five-membered enecarbamates with overall yields of 23% and 26%, respectively. The synthetic strategy made use of a highly effective and stereoselective [2+2]cycloaddition of enantiomerically pure endocyclic enecarbamates with dichloroketene, as well as an efficient decarboxylation step of a bicyclic a-amino acid employing Boger's acyl selenide protocol employing tributyltin hydride. Interesting aspects concerning the regiochemical outcome of Baeyer-Villiger oxidations of bicyclic cyclobutanones are also reported, in which the usual stereoelectronic bias of Baeyer-Villiger oxidation seems to be counterbalanced by steric effects on the putative Criegee intermediate.

【 授权许可】

Unknown