and evaporated the crude product weighed 7 0 g 90 of theory and was used in step 9 without further purification the fab m s showed a molecular ion peak at 647 to a mixture of 4s 5r 1 39 r 3 39 e 2 2 3 trimethyl 5 1 39 methyl 3 39 pentenyl 4 oxazolidinecarboxylic acid prepared by heating at reflux temperature a solution of 2s 3r 4r 6e 3 hydroxy 4 methyl 2 methylamino 6 octenoic acid prepared by the process set forth in r m wenger helv chim acta 66 1983 2308 250 mg 1 24 mmol in dry acetone 80 ml for 24 hours and subsequent evaporation under diminished pressure in 1 ml acetone were added successively with stirring under a nitrogen atmosphere dry tetrahydrofuran 10 ml n methylmorpholine 152 u03bcl 1 40 mmol n hydroxybenzotriazole 335 7 mg 2 48 mmol and l 2 aminobutyryl sarcosyl n methyl l leucyl valyl n methyl l alanyl l alanine benzyl ester 803 mg 1 24 mmol the reaction mixture was cooled in an ice bath and 1 3 dicyclohexylcarbodiimide 267 8 mg 1 30 mmol added the mixture was allowed to attain room temperature and stirring was continued for an additional 24 hours the mixture was diluted with dichloromethane 60 ml and washed with saturated sodium.