| 摘要 |
<p>A carboxylic acid of the formula R1-COOH (R1=III or IV; R3=acyl; R4=H, alkoxy or alkylthio; R5=Me, halo, acethoxymethyl or (1- methyltetrazol-5-yl) thiomethyl; X=O,S or -CH2-; R2=diphenyl methyl, 2,4,6-trimethylbenzyl or p-methoxybenzyl) is prepd. by reacting a corresponding ester of the formula R1-COOR2 with a lower alkylthiol and a Lew is acid. The process provides a method for the deesterification of carboxylic acid esters which is unusally mild and efficient, and is useful in the synthesis of penicillins and cephalosporins in which a carboxylic acid gp. is protected by esterification during the synthesis.</p> |
