Enantioselective Synthesis of 3,4-Disubstituted cis- and trans-1,2,5-Thiadiazolidine-1,1-dioxides as Precursors for Chiral 1,2-Diamines
摘要:
Both, cis- and trans-3,4-disubstituted thiadiazolidines 5 and 6 can enantioselectively be obtained from thiadiazoles 2 which, in turn, are efficiently prepared from the respective 1,2-diketone by an improved protocol. An asymmetric ruthenium-catalyzed transfer hydrogenation followed by a diastereoselective hydride addition furnishes exclusively the cis-isomers 5 which, under acidic conditions, undergo a novel isomerization into the trans-isomers 6. These cyclic sulfamides can be transformed into 1,2-diamines as well as 2,3-diamino acids.
Process for the preparation of 7-amino and 7-substituted
申请人:Gema, S.A.
公开号:US04767851A1
公开(公告)日:1988-08-30
An improved process is disclosed for the preparation of 7-amino and 7-substituted amino-desacetoxycephalosporins in which the corresponding 6-substituted amino penicillin sulphoxide is heated in the presence of an acidic substance which causes expansion of the penam ring in the reactant to the .DELTA..sup.3 cephem ring in the product in the presence of a silicon containing compound. The process comprises adding sulphamide or a silylsulphamide or a silylsulphamoyl to the reaction or utilizing a silylsulphamide or silylsulphamoyl as the silicon containing compound.