Conformation changes induced in 2‐spiro‐substituted cephalosporin sulphoxides by the configuration of the spiro bond: A combined ¹H and ¹³C NMR study

Abstract

1,3-Dipolar cydoadditions of diazomethane and diphenyldiazomethane to exo-2-methylenecephalosporios are described. A structmal study of the products shows that the initially formed 2-spiropymzolinocephems form cydopropanes by the spontaneous loss of nitrogen. ASIS and NOE measurements reveal that the products with different C-2 configurations are in two different conformations.

Olivanic acid analogues. Part 4. Cycloaddition reactions of p-nitrobenzyl 7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate, and synthesis of the 8-oxo-1-azatricyclo[4.2.0.02,4]octane-2-carboxylate system

“…In order to incorporate into our synthesis a 3-sulphur substituent, a feature which is characteristic of the olivanate natural products, we have demonstrated that the double bond present in compound (1) reacts with thiols as a Michael acceptor.6 Reintroduction of the double bond using (di-ch1oroiodo)benzene gave access either to a A2-3-sulphinyl derivative,6 or to a mixture of the corresponding A2-and A3sulphenyl compounds' [e.g. (19), (20)], according to the oxidative conditions employed.…”