I the tert-butyldimethylsilyl-protectedll threonine 8 to the corresponding acid chloride (oxalyl chloride/DMF) 12 followed by reaction with triphenylmethanesufenamide 9b provided the desired thiohydroxamate 10. Unfortunately, removal of the silyl protecting group (n-Bu, NF) to provide 11 followed by attempted cyclization under modified Mitsunobu conditions (Ph3P/CC14/Et3N) did not provide any of the desired 0-lactam 13.13 In contrast, the O- ...