Protection of hydroxyl in the synthesis of semisynthetic beta-lactam antibiotics

The 2-methoxypropan-2-yl group fulfills the need of a hydroxyl protecting group generally suitable for the synthesis of beta-lactam antibiotics, satisfying the criteria of low-cost, convenience and selectivity in formation, and, above all, ease of deprotection under conditions compatible to the highly sensitive beta-lactam function and without contamination of the final products. The use of this protecting group has enabled the successful attachment of 6-[4-(N-acetyl-4-hydroxyl-L-prolylamino)phenyl]-1,2-dihydro - 2 - oxo - 3 - pyridinecarboxyl group, through an amide linkage, to amoxicillin, cephaloglycin, and the 3[[(1-carboxymethyl)-1-H-tetrazol-5-yl]thio]methyl analogue of the latter, yielding broad-spectrum antibiotics with notably good activities against strains of Pseudomonas aeruginosa.