Yuji Oikawa

Specific removal of o-methoxybenzyl protection by DDQ oxidation.

Abstract Methoxybenzyl protecting groups of alcohols were readily and efficiently removed with DDQ in CH2Cl2-H2O at room temperature. Under these neutral conditions, other usual protecting groups, isopropylidene, methoxymethyl, benzyloxymethyl, tetrahydropyranyl, acetyl, t-butyldimethylsilyl, benzyl, benzoyl, and tosyl, as well as functional groups, epoxide, double bond, and ketone, were remained unchanged.

On the selectivity of deprotection of benzyl, mpm (4-methoxybenzyl) and dmpm (3,4-dimethoxybenzyl) protecting groups for hydroxy functions

Abstract The 4-methoxybenzyl (MPM) protecting group for hydroxy functions is readily removed with DDQ in dichloromethane containing a small amount of water at room temperature. Under these neutral conditions, several other protecting and functional groups remained unchanged. 3,4-Dimethoxybenzyl (DMPM) groups are more reactive than MPM groups with DDQ. The benzyl (Bn) protecting group was removed by catalytic hydrogenation over Raney nickel. Selective deprotection of DMPM, MPM and Bn groups is also presented.

Selective hydrogenolysis of the benzyl protecting group for hydroxy function with Raney nickel in the presence of the MPM (4-methoxybenzyl) and DMPM (3,4-dimethoxybenzyl) protecting groups

Abstract The benzyl protecting group for hydroxy function was selectively removed by catalytic hydrogenolysis with Raney nickel in the presence of the MPM (4-methoxybenzyl) and DMPM (3,4-dimethoxybenzyl) protecting groups, and applied to the synthesis of some synthons to macrolide and polyether antibiotics.

DMPM (3,4-dimethoxybenzyl) protecting group for hydroxy function more readily removable than MPM (p-methoxybenzyl) protecting group by DDQ oxidation

Abstract The DMPM (3,4-dimethoxybenzyl) protection for hydroxy function was deprotected more readily than the MPM (p-methoxybenzyl) protection by DDQ oxidation under neutral conditions, and applied to the synthesis of some synthons to macrolide and polyether antibiotics.

A stereoselective total synthesis of (9S)-9-dihydroerythronolide A from D-glucose☆

Abstract A rather facile stereoselective total synthesis of (9S)-9-dihydroerythronolide A starting from D-glucose was achieved via coupling of C1-C6 and C7-C15 segments and subsequent macrolactonization.

Kinetic acetalization for 1,2- and 1,3-diol protection by the reaction of p-methoxyphenylmethyl methyl ether with DDQ

Abstract When 1,2- and 1,3-diols were treated with p-methoxyphenylmethyl methyl ether (MPMME) in the presence of DDQ, the kinetically controlled oxidative acetalization occurred smoothly even in case of acid-labile compounds to give p-methoxybenzylidene acetals rather stereoselectively.

Highly stereoselective synthesis of methynolide, the aglycone of the 12-membered ring macrolide methymycin, from D-glucose

Abstract A highly stereoselective and efficient synthesis of methynolide, the aglycone of 12-membered macrolide methymycin, was achieved from of C1–C8 and C9–C13 segments synthesized from D-glucose by employing some stereoselective reactions and benzyl-type protecting groups.

Total synthesis of tylonolide, the aglycone of the 16-membered ring macrolide tylosin, from D-glucose. Selective application of MPM and DMPM protecting groups for hydroxy functions☆

Abstract Segments i (C11–C17) and ii (C1–C10), synthesized from D-glucose by employing some stereoselective reactions and benzyl-type protecting groups, were esterified and cyclized to the 16-membered enone, which was readily converted to tylonolide, the aglycone of tylosin.

Stereoselective synthesis of the middle (C10–C17) and right (C18–C30) segments and their coupling to complete a formal synthesis of the polyether antibiotic salinomycin☆

Abstract The middle (C10–C17) and right (C18–C30) segments of the polyether antibiotic salinomycin were stereoselectively synthesized from D-glucose, D-mannitol and ethyl L-lactate. Coupling of the two segments followed by construction of the bisketal ring system gave the C10–C30 segment, which was already converted to salinomycin by Kishi.

Cyclization of β-ketosulfoxide—III: Synthesis of naphthalene and phenanthrene derivatives

Abstract On heating with trichloroacetic acid or trifluoroacetic acid, 2,4-dimethoxyphenethyl methylsulfinylmethyl ketone (1) cyclized to 2,3-dimethoxy-5-methylthio-6-oxo-5, 6, 7, 8-tetrahydronaphthalene (2) through an intramolecular nucleophilic substitution of a sulfonium ion intermediate (20b), while a β -ketosulfoxide having naphthalene nucleus (3) cyclized to a tetrahydrophenanthrene 4 via a Pummerer rearrangement product 23. Treatment of 1 with p-toluenesulfonic acid gave a mixture of 2,3,6-trisubstituted naphthalenes (7–10), whose composition was dependent on the reaction conditions. The aromatization proceeded via 2.