Debenzylation preferential

Pfenninger s. Staudinger Pfitzner-Moffati reagent 21, 284 pH s. Buffer solns.. Regulators 2-Phase medium, reactions in -0-debenzylation, preferential 22,11 oxidation 21, 730 Phenacetyl chloride as reagent 22, 535... 

Quebrachitol was converted into iL-c/j/roinositol (105). Exhaustive O-isopropylidenation of 105 with 2,2-dimethoxypropane, selective removal of the 3,4-0-protective group, and preferential 3-0-benzylation gave compound 106. Oxidation of 106 with dimethyl sulfoxide-oxalyl chloride provided the inosose 107. Wittig reaction of 107 with methyl(triphenyl)phos-phonium bromide and butyllithium, and subsequent hydroboration and oxidation furnished compound 108. A series of reactions, namely, protection of the primary hydroxyl group, 0-debenzylation, formation of A-methyl dithiocarbonate, deoxygenation with tributyltin hydride, and removal of the protective groups, converted 108 into 7. 

Cyclization of the bis-epoxides 123 (mixtures of diastereomers) with benzylamine afforded the azepanes 124 in a preferential 1-endo-tet methodology (Equation 17) <1995JOC5958> however, with the corresponding 3,4-benzyl ethers of the bis-epoxides rather than the // / -acetonide protecting group, no cyclization to six-membered ting species was observed. The azepanes 124 were then converted in two steps to the amino sugar hydrochloride salts 126 via the N-debenzylated intermediates 125 (Scheme 16). 

BnBr/K2C03 in DMF versus BnBr/NaH in THF), refinement of the work-up procedure for the Dess-Martin oxidation of per-0-benzylcatechin (50) (Scheme 7), replacement of TiCl4 by Bentonite clay K-10 for the coupling of the benzylated flavan-3-ol and flavan-3,4-diol equivalent, such as (52) and (95) (Scheme 15), and most notably, using an EtOAc/water mixture for the catalytic debenzylation step. Such a biphasic solvent system permitted preferential dissolution of the per-0-benzyl procyanidin, such as (96), in the EtOAc layer, and of the free phenolic compound, such as (5), in the water layer. 

Hydrogen bromide Ring closure of acetals with preferential O-debenzylation Quinolizinium ring... 

Preferential debenzylation of carboxylic acid esters s. 16,621 COOCHgCeHs COOH... 

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