A diastereo- and enantioselective approach to functionalized 3,4-cis-β-lactams 9 and 16 was developed based on the use of chiral norephedrine-derived oxazolidines. The key-steps in the synthesis of 9 (Scheme 1) are the potassium hypochlorite epoxidation of aldehyde 1 and the lithium dimethylcuprate addition to acid 2, both steps proceed regio- and stereoselectively (98%) and in high yield. Standard synthetic methods and the Miller hydroxamate procedure for NC cyclization were used to complete the synthesis of the target cis-β-lactwn 9 (98% enantiomeric excess). In the synthesis of cis-substituted 3-amino-2-azetidinone 16 (Scheme 4) the key-step is the aqueous ammonia opening of epoxy acid 2 which proceeds regio- and stereoselectively (98%). The Miller-type cyclization of hydroxamate 15a under Mitsunobu conditions failed to give 16a in a yield higher than 35%.
ASYMMETRIC-SYNTHESIS OF 3,4-CIS-SUBSTITUTED BETA-LACTAMS VIA CHIRAL NOREPHEDRINE-DERIVED OXAZOLIDINES / S. CARDANI, C.M.A. GENNARI, C. SCOLASTICO, R. VILLA. - In: TETRAHEDRON. - ISSN 0040-4020. - 45:23(1989), pp. 7397-7404.
ASYMMETRIC-SYNTHESIS OF 3,4-CIS-SUBSTITUTED BETA-LACTAMS VIA CHIRAL NOREPHEDRINE-DERIVED OXAZOLIDINES
C.M.A. GENNARISecondo
;C. SCOLASTICOPenultimo
;
1989
Abstract
A diastereo- and enantioselective approach to functionalized 3,4-cis-β-lactams 9 and 16 was developed based on the use of chiral norephedrine-derived oxazolidines. The key-steps in the synthesis of 9 (Scheme 1) are the potassium hypochlorite epoxidation of aldehyde 1 and the lithium dimethylcuprate addition to acid 2, both steps proceed regio- and stereoselectively (98%) and in high yield. Standard synthetic methods and the Miller hydroxamate procedure for NC cyclization were used to complete the synthesis of the target cis-β-lactwn 9 (98% enantiomeric excess). In the synthesis of cis-substituted 3-amino-2-azetidinone 16 (Scheme 4) the key-step is the aqueous ammonia opening of epoxy acid 2 which proceeds regio- and stereoselectively (98%). The Miller-type cyclization of hydroxamate 15a under Mitsunobu conditions failed to give 16a in a yield higher than 35%.Pubblicazioni consigliate
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