Intramelanocytic Acidification Plays a Role in the Antimelanogenic and Antioxidative Properties of Vitamin C and Its Derivatives

Figure 1

Synthetic route of MAP and AAE. (i) The first step in the synthesis of both compounds was protection of the 5,6-position hydroxy of VC. VC was reacted with three equivalents of acetone to form 5,6-O-isopropylidene-L-VC under catalysis of 0.1 equivalent of Lewis acid. (ii) 5,6-O-isopropylidene-L-VC was reacted with 1.1 equivalents of ethyl bromide to form the 3-O-ethylated intermediate. (iii) The 3-O-ethylated intermediate was hydrolyzed with 0.1 equivalent mineral acid to form AAE. (iv) 5,6-O-isopropylidene-L-VC was reacted with phosphorus oxychloride to form the phosphate intermediate under alkaline conditions. (v) The phosphate intermediate was deprotected by acid hydrolysis to form VC-2-phosphate, after which it was reacted with magnesium oxide to form MAP.