The labile tert-butyldimethylsilyl esters of the azetidinones 6-8b served as the crucial synthons in the preparation of the potentially useful ylide pyridyl thio esters 18-20. These intermediates were utilized to synthesize a host of title carbapenems 25-30d, 32, and 49-53. The antimicrobial properties and DHP-I susceptibility of these carbapenems were studied with reference to thienamycin.