2-(Prenyloxymethyl)benzoyl (POMB) as a new temporary protecting group for alcohols

The 2-(prenyloxymethyl)benzoyl (POMB) group was introduced in high yields to hydroxyl functions using the crystalline reagent, 2-(prenyloxymethyl)benzoic acid, in the presence of dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). 2-(Prenyloxymethyl)benzoic acid is readily available, in two steps, from phthalide in 65% overall yield. The POMB group can be cleaved, in two steps, by treatment with 2,3-dichloro-5,6-dicyanoquinone (DDQ) followed by intramolecular lactonisation of the resulting hydroxy ester induced by a catalytic amount of Yb(OTf)₃·H₂O. The reaction conditions are compatible with the presence of a number of protecting groups such as isopropylidene, benzyl, acetyl, chloroacetyl, benzoyl, levulinoyl, Fmoc and Boc groups.