Trifluoroacetic acid → HCID 70602156, compound

Participants

Reaction Steps

A mixture of 0.025 g of the isomer B of α-(3,3-dimethyl-7-oxo-4-thia-2,6-diaza-6-bicyclo[3,2,0]heptyl)-α-(carboxymethyl)-acetic acid tert.-butyl ester (Example 39) and 1 ml of trifluoroacetic acid is kept for 18 hours at 0°, is then evaporated under reduced pressure, and the residue containing the α-(3,3-dimethyl-7-oxo-4-thia-2,6-diaza-6-bicyclo[3,2,0]heptyl)-α-(carboxymethyl)-acetic acid, is taken up in 1 ml of dioxane and then mixed with an ether solution of diazomethane until saturated. After 3 minutes reaction time, the mixture is evaporated under reduced pressure and the residue is filtered through a silica gel column (diameter: 0.8 cm; hight: 10 cm), a 2:1-mixture of hexane and ethyl acetate being used for elution; the isomer B of α-(3,3-dimethyl-7-oxo-4-thia-2,6-diaza-6-bicyclo[3,2,0]heptyl)-α-(carbomethoxymethyl)-acetic acid methyl ester of the formula ##STR56## which is obtained as a crude product, melts at 136°-137° after recrystallisation from a mixture of ether, methylene chloride and hexane.

Provenance & Evidence