Penicillin esters and their preparation

A class of esters of the penicillin, nafcillin have the general formula: wherein A is a C1-C6 alkylene group substituted with one or two groups of formula -NR1 R2 and optionally further substituted with one or more methyl or ethyl groups, wherein R1 and R2 are the same or different and each is a C1-C6 alkyl group or R1 and R2 together with the nitrogen atom to which they are attached form a saturated 5- or 6- membered heterocyclic ring. Upon oral administration, the esters are absorbed into the bloodstream where they are hydrolyzed to release the antibacterially active parent penicillin, nafcillin.