Tsutomu Sugahara

An enantioconvergent route to (−)-kainic acid

Abstract A new stereocontrolled route to (−)-kainic acid, the representative of the kainoid amino acids and exhibiting insecticidal, anthelmintic and neuroexcitatory properties, has been devised in an enantioconvergent way using either (+)- or (−)-ketodicyclopentadiene as the starting material by employing a concurrent retro-Diels-Alder reaction and intramolecular ene reaction as the key step.

Oxidative resolution of 2-cyclopentenols by the asymmetric hydrogen transfer protocol

A RuII-chiral amine complex has accomplished oxidative resolution of the 2-cyclopentene-1-ols having a bicyclo[2.2.1]heptene background to afford the cyclopentenones and the cyclopentenols both in good to excellent optical and chemical yields by an asymmetric hydrogen transfer reaction. The hydrogen transfer occurred selectively at the allylic methine hydrogen even though allylic methylene hydrogens are present at the same relative position.

Enantioconvergent synthesis of (+)-estrone from racemic 4-tert-butoxy-2-cyclopentenone

Abstract (+)-Estrone has been synthesized in an enantioconvergent manner from racemic 4- tert -butoxy-2-cyclopentenone via contrasteric Diels-Alder reaction and lipase-mediated kinetic transesterification as the key steps.

A new stereocontrolled route to (+)-curcuphenol, a phenolic sesquiterpene from the marine sponge Didiscus flavus

Abstract Using a synthetic equivalent of chiral 2-cyclopentenol, (+)-curcuphenol, a cytotoxic bisabolane type sesquiterpene isolated from the marine sponge Didiscus flavus, has been synthesized through a concurrent retro-Diels–Alder reaction and Claisen rearrangement reaction.

Studies on total photolytic synthesis of alkaloids—III : The products of photo-pschorr reaction—total synthesis of isocorydine

Abstract A comparison of photolysis and thermal decomposition of the 1-(2-amino-3-benzyloxy-4-methoxybenzyl)-6-benzyloxy-1,2,3,4-tetrahydro-7-methoxy-2-methylis (8) is described together with the synthesis of N-methyllindecarpine (28) by photolysis and the synthetic trials of codeine and sinomenine.

Biogenetic type syntheses of aporphine alkaloids, isoboldine and glaucine

Abstract Phenolic oxidative coupling of N-ethoxycarbonylnorreticuline ( 15 ) with potassium ferricyanide gave 6-ethoxycarbonyl-1,9-dihydroxy-2,10-dimethoxyaporphine ( 19 ), which was also obtained by phenolic oxidative coupling of 1-(2-bromo-5-hydroxy-4-methoxybenzyl)-2-ethoxycarbonyl 1,2,3,4-tetrahydro-7-hydroxy-6-methoxyisoquinoline ( 16 ), the Br atom being eliminated during the reaction. Reduction of this aporphine ( 17 ) gave the isoboldine ( 3 ), which was methylated with diazomethane to afford the glaucine ( 4 ).

Stereocontrolled approach to acromelic acids

Abstract A potential stereocontrolled route to acromelic acids, neuroexitatory amino acids isolated from the mushroom Clitocybe acromelalga , has been developed by employing either concurrent Chugaev-ene reaction or retro-Diels–Alder-ene reaction and regioselective pyridinecarboxylate formation reaction as the key steps.

Total syntheses of (±)-pronuciferine, (±)-O-methylorientalinone, and (±)-O-methylkreysiginone

Abstract Photolysis of 8-bromo-1,2,3,4-tetrahydro-1-(4-hydroxybenzyl)-6,7-dimethoxy-2-methyl-isoquinoline (21) gave (±)-pronuciferine (2). The same reaction of the phenolic bromoisoquinoline (20 and 23) afforded (±)- O -methylorientalinone (3a or 3b) and (±)- O -methylisoorientalinone (3b or 3a). and (±)- O -methylkreysiginone (5a or 5b).

Contra-steric Diels-Alder route to 3-oxodicyclopentadiene and meso 3,5-endo-dihydroxy-4,5-dihydrodicyclopentadiene

Abstract Diels-Alder reaction between cyclopentadiene and 4- tert -butoxycyclopentenone occurs in a contra-steric manner to give more hindered endo -3- tert -butoxydicyclopentadiene as the major product (∼15:1) in excellent yield. The product has been transformed into either (±)- and (−)-3-oxodicyclopentadiene or meso 3,5- endo -dihydroxy-4,5-dihydrodicyclopentadiene efficiently.

Studies on the syntheses of heterocyclic compounds. Part 678. Photoracemisation and photoepimerisation of the phthalidylisoquinoline alkaloids (–)-α-narcotine and (–)-β-hydrastine

Irradiation of (–)-α-narcotine (3) in tetrahydrofuran gave a mixture of racemates of two epimers, (±)-α-narcotine (5) and (±)-β-narcotine (7). Similarly, irradiation of (–)-β-hydrastine (4) afforded (±)-α-hydrastine (8) and (±)-β-hydrastine (6).