Studies related to penicillins. Part 25. Synthesis of N-phenylacetyl and N-triphenylmethyl derivatives of 6-aminopenam 1-oxides

Abstract

In boiling benzene, (3R,4R)-1-methylallyl-3-phenylacetamido-4-t-butylsulphinylazetidin-2-one (11a) is converted into (1S,5R,6R)-2,2-dimethyl-6-phenylacetamidopenam oxide (9a). (3R,4R)-1-Methylallyl-4-t-butylsulphinyl-3-triphenylmethylaminoazetidin-2-one (11b) and its (3R,4S)-diastereoisomer (18) react in an analogous manner to give (1S,5R,6R)-2,2-dimethyl-6-triphenylmethylaminopenam 1-oxide (9b) and its (1R,5S,6R)-diastereoisomer (16). 3-Methylallyl-5-triphenylmethyliminothiazolidin-4-one (12), whose structure has been established by X-ray crystallography, is also formed in the thermal reactions of compounds (11b) and (18).

The thermolysis of (3R,4R)-1-allyl-3-phenylacetamido-4-t-butylsulphinylazetidin-2-one (11c) and its 3-triphenylmethylamino counterpart (11d) gives rise to (1S,2S,5R,6R)-2-methyl-6-phenylacetamidopenam 1-oxide (9d) and its 6-triphenylmethylamino relative (9e). However, no bicyclic β-lactam derivatives are isolated from the N-phenylacetyl and N-triphenylmethyl derivatives (21a,b) of (3R,4R)-3-amino-1-prop-2-ynyl-4-t-butylsulphinylazetidin-2-one under thermal conditions.