Synthesis and characterization of 6-O-acyl-2-O-α-D-glucopyranosyl-L- ascorbic acids with a branched-acyl chain

We previously reported the chemical synthesis of a series of novel monoacylated vitamin C derivatives, 6-O-acyl-2-O-α-D-glucopyranosyl-L- ascorbic acids (6-Acyl-AA-2G) possessing a straight-acyl chain of varying length from C₄ to C₁₈, as effective skin antioxidants. In this paper, we describe branched type of 6-Acyl-AA-2G derivatives (6-bAcyl-AA-2G) synthesized by use of a 2-branched-chain fatty acid anhydride as an acyl donor. The stability of 6-bAcyl-AA-2G in neutral solution was much higher than that of 6-Acyl-AA-2G, while they were susceptible to enzymatic hydrolysis for exerting vitamin C effect. These branched derivatives as well as 6-Acyl-AA-2G increased the radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl and the lipophilicity in octanol/water-partitioning systems with increasing length of their acyl group. In addition, the 6-bAcyl-AA-2G derivative with an acyl chain of C₁₂, 6-bDode-AA-2G had the excellent solubility to various solvents, suggesting easy handling in cosmetic use. These characteristics of 6-bAcyl-AA-2G may be available for skin care application as an effective antioxidant.