Inhibitory effects of 6-O-acylated l-ascorbic acids possessing a straight- or branched-acyl chain on Epstein–Barr virus activation

6- O - Acylated l -ascorbic acids possessing a straight- or branched-acyl chain of varying length from C 4 to C 18 have been synthesized and evaluated their anti-tumor promoting effects on the activation of the Epstein–Barr virus early antigen. The derivatives having a straight- or branched-acyl chain of C 6 to C 11 carbon atoms exhibited marked effects.