ABSTRACT
Ylidene derivatives of sugars are important intermediates in synthetic carbohydrate chemistry. They are most often formed from sugars and carbonyl compounds or their dialkyl acetals under anhydrous conditions in presence of acid catalyst. Deprotection is done frequently by acid hydrolysis.1,2 Benzylidene protecting groups are of special importance because they can be removed under nonhydrolytic conditions, by catalytic hydrogenolysis. O-p-methoxybenzylidene group offers possibility for more sophisticated orthogonal protection, as this group can be selectively removed in the presence of benzylidene acetal under both nonhydrolytic and nonreductive conditions by treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ),3 ceric ammonium nitrate (CAN),4 or SnCl4 and thiophenol.5
