Nobuo Nakazaki

Regioselective O-deacylation of fully acylated glycosides and 1,2-O-isopropylidenealdofuranose derivatives with hydrazine hydrate

Abstract On hydrazinolysis in 1:4 acetic acid-pyridine, and in pyridine, partial O -deacylation of fully acylated methyl glycosides and some other glycosyl compounds (23 compounds) was found to be induced, to give, in good yields, products bearing one free hydroxyl group; the results obtained indicated that, among the primary and secondary O -acyl groups, the 2- O -acyl groups were, in general, the most labile toward the nucleophile (hydrazine). Hydrazinolysis of 1,2- O -isopropylidenealdofuranose acylates (3 compounds), on the other hand, gave, in high yield, the corresponding monoacyl derivatives having the protecting group on their primary hydroxyl group. The factors possibly involved in the regioselectivity of the hydrazinolysis were discussed.

Novel procedure for regioselective 2′-O-deacylation of fully acylated purine and pyrimidine ribonucleosides with hydrazine hydrate

Hydrazinolysis of N6, N6,2′,3′,5′-pentabenzoyladenosine, N2,2′,3′,5′-tetrabenzoylguanosine, and 2′,-3′,5′-tri-O-benzoylinosine in AcOH-pyridine was regio-selectively induced at the 2′-position among the three alcoholic functions to give the corresponding 2′-OH derivatives in good yields; this procedure also proved effective for the partial debenzoylation of fully benzoylated uridine and cytidine although the regioselectivity observed was not as good.

Fusion reactions, involving activating agents, of some purine derivatives with 1,3,4,6-tetra-O-acetyl- 2-acylamido-2-deoxy-β-d-glucopyranoses

Abstract Fusion of 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β- d -glucopyranose, 1,3,4,6-tetra-O-acetyl-2-deoxy-2-phthalimido-β- d -glucopyranose, and 1,3,4,6-tetra-O-acetyl-2-benzamido-2-deoxy-β- d -glucopyranose with 2,6-dichloropurine, theophylline, and 6-benzylaminopurine in activating agents afforded the corresponding aminonucleosides in good yields. The simultaneous formation of a positional isomer was confirmed in three examples in the reactions with 2,6-dichloropurine and 6-benzylaminopurine. On the basis of these results, the potential effect of 2-acylamido functional groups on the reaction is discussed.

Partial protection of carbohydrate derivatives. Part 1. Specific N-debenzoylation of fully benzoylated adenosine and cytidine with phenols and alcohols; active N-benzoyl groups

Specific N-debenzoylation of N6,2′,3′,5′-tetrabenzoyladenosine (1), N6,N6,2′,3′,5′-pentabenzoyladenosine (3), and N4,2′,3′,5′-tetrabenzoylcytidine (4) was achieved by treatment with nitrophenols, phenol, p-methoxyphenol, and a series of alcohols to give the corresponding nucleoside benzoates with free amino-groups in high yields: the reaction can also be regarded as a benzoylation of hydroxy-compounds by nucleoside N-benzoyl groups. On the basis of these results, the order of activity of these nucleoside benzoates was found to be (3) > (1) > (4). N-Benzoylation of 2′,3′,5′-tri-O-benzoyladenosine (2) with 2,4-dinitrophenyl benzoate (5) and of cytidine (6) with the pentabenzoyladenosine (3) gave the tetrabenzoyladenosine (1) and N-benzoylcytidine (7), respectively, in high yields.