Cycloadditions of highly functionalized C6-synthons to cyclic nitrones
作者:Montserrat Closa、Pedro de March、Marta Figueredo、Josep Font、Angeles Soria
DOI:10.1016/s0040-4020(97)10083-7
日期:1997.12
The 1,3-dipolar cycloaddition of cyclic nitrones to several C6 α,β-unsaturated esters and lactones with different functionalities has been studied. All these olefins have shown high stereoselectivity, with a predominance of the exo or endo transition state for the cis or trans dipolarophiles, respectively. The antifacial approach is favoured in the reactions with γ-substituted hexenolides and also
γ-Lactam analogues of penicillanic and carbapenicillanic acids
作者:Jack E. Baldwin、Ming Fai Chan、Gerard Gallacher、Masami Otsuka、Peter Monk、Keith Prout
DOI:10.1016/s0040-4020(01)98828-3
日期:——
(12a) and (12b) in a ratio of 85 : 15. They are transformed to the carbapenam analogues (1)-(4). Their stereochemistry was assigned according to the X-ray structure of the γ-lactam (12b). Benzyl 6-oxopenicillanate (20) was directly transformed to the γ-lactamanalogue (5) a novel ring expansion. These synthetic analogues did not show antibiotic activity or β-lactamase inhibition. Treatment of pyrro1idine-2