Masayuki Sakakibara

Synthesis of naturally occurring brassinosteroids employing cleavage of 23,34-epoxides as key reactions. Synthesis of brassinolide, castasterone, dolicholide, dolichosterone, homodolicholide, homodolichosterone, 6-deoxocastasterone and 6-deoxodolichosterone☆

Abstract Eight new plant growth-promoting steroids (brassinolide, castasterone, dolicholide, dolichosterone, homodolicholide, homodolichosterone, 6-deoxocastasterone and 6-deoxodolichosterone) were synthesized by the regio- and stereoselective ring-opening reactions of 23,24-epoxides prepared from stigmasterol.

Synthesis of (22S, 23S)-homobrassinolide and brassinolide from stigmasterol

Abstract (22S, 23S)-Homobrassinolide (2α, 3α, 22S, 23S-tetrahydroxy-24S-etyl-B-homo-7-oxa-5α-cholestan-6-one) and brassinolide (2α, 3α 22R, 23R-tetrahydroxy-24S-methyl-B-homo-7-oxa-5α-cholestan-6-one) were synthesized from stigmasterol and shown to promote plant growth.

S1319: A novel β2-adrenoceptor agonist from a marine sponge Dysidea sp.

In the course of screening of potential leads for beta2-receptor agonists, we found a novel beta2-adrenoceptor selective agonist, S1319, from a marine sponge Dysidea sp. The active compound was isolated and structurally characterized as 4-hydroxy-7-[1-(1-hydroxy-2-methylamino)ethyl]-1,3-benzothiazole-2(3H)-o ne, a new member of the beta2-adrenoceptor agonist. This is the first example of a sponge-derived beta2-adrenoceptor agonist.

Synthesis of a stereoisomeric mixture of 2,3-dihydro-2,3,5-trimethyl-6-(1-methyl-1-oxobutyl)-4H-pyran-4-one, the pheromone of the drugstore beetle

Abstract Reaction of acetaldehyde with the trianion of 4,6-dimethylnonane-3,5, 7-trione followed by acidification yielded a stereoisomeric mixture of the pheromone of Stegobium paniceum L.

Synthesis of (2s, 3r, 7rs)-stegobinone [2,3-dihydro-2,3,5-trimethyl-6-(1-methyl-2- oxobutyl)-4h-pyran-4-one] and its (2r, 3s, 7rs)-isomer : The pheromone of the drugstore beetle

Abstract Reaction of acetaldehyde with the trianion of 4,6-dimethylnonane-3,5,7-trione followed by acidification yielded a stereoisomeric mixture of stegobinone, the pheromone of Stegobium paniceum L. Acylation of the dianion derived from 4-methylheptane-3,5-dione with a mixed anhydride prepared from (2R, 3S)-3-hydroxy-2-methylbutanoic acid or its enantiomer led to (2S,3R,7RS)- or (2R, 3S, 7RS)-stegobinone. The natural pheromone possesses (2S,3R)-stereochemistry.

PD-CATALYZED ALLYLIC ALKYLATION OF PHENYLVINYLCARBINOLS WITH SOME NUCLEOPHILES

Abstract Allylic alkylation of phenylvinylcarbinols with various nucleophiles proceeded smoothly under mild reaction conditions in the presence of Pd(PPh 3 ) 4 providing an efficient methodology for the synthesis of estrogens and their analogs.

Synthesis of arnebinol, an ansa-type prenylated phenol with effects inhibitory to prostaglandin biosynthesis

Abstract Arnebinol, a new ansa-type prenylated phenol, was synthesized in 12 steps from geraniol and p-benzoquinone in 5.1 % overall yield.

A novel method for regio- and stereoselective hydroxylation of anthracycline glycosides

Abstract Hydroxylation at C-10 position of anthracycline glycoside proceeds stereoselectively with trimethylamine-N-oxide in DMF.

An approach to stereoselective formation of glycinoeclepin a side chain

Abstract Claisen rearrangement was found to be an efficient method for the stereoselective construction of the glycinoeclepin A side chain.

Facile Synthesis of (22R, 23R)-Homobrassinolide

A synthesis of (22R,23R)-homobrassinolide is described. The LC and the chemical correlation studies for the oxidation product of a stigmasterol-like side chain with osmium tetroxide are mentioned. A stereochemical view for the mechanism of osmium tetroxide oxidation of the side chain is proposed.