Akio Furusaki

Teurilene and thyrsiferyl 23-acetate, meso and remarkably cytotoxic compounds from the marine red alga laurencia obtusa (hudson) lamouroux

Abstract Two new cyclic ethers consisting of squalene carbon skeleton have been isolated from the red alga L. obtusa . The absolute stereostructure of teurilene ( 1 ) was elucidated by x-ray crystallographic method, and the structure of thyrsiferyl 23-acetate ( 2 ) was established from the spectral and chemical evidence.

The absolute configurations of halogenated chamigrene derivatives from the marine alga, laurencia glandulifera kützing

Abstract The absolute configurations of halogenated chamigrene derivatives, isolated from L. glandulifera Kutzing, 10-bromo-3,4-epoxy-α-chamigrene (1), glanduliferol (2), 10-bromo-α-chamigren-4-one (3), 4,10-dibromo-3-chloro-α-chamigrene (4) and 10-bromo-α-chamigrene (5), have been determined by X-ray diffraction analysis of 1 and subsequently, by relating 2, 3, 4 and 5 to 1 with the chemical methods. In addition, the absolute configuration of (−)-α-chamigrene (6), yielded on the process of the above chemical transformation, has been elucidated.

Cyclization of aminyl radicals generated by anodic oxidation of lithium alkenylamides. Stereo- and regioselective synthesis of cis-l-alkyl-2, 5-disubstituted pyrrolidines

Abstract Neutral aminyl radicals (3) generated by anodic oxidation of lithium alkenylanides (2) were found to undergo a stereo- and regioaelective cyclization to give cis -1-alkyl-2, 5-disubatituted pyrrolidines (5c–5h) in moderate yields. The cis stereochemistry of 5c–5h was confirmed by comparison with the corresponding trans -1-allkyl-2, 5-disubstituted pyrrolidines which were prepared by aminomercuration of 1c–1h. The structure of trans -1,2-dimethyl-5-phenylpyrrolidine (17) was established by an X-ray crystallographic analysis of its ammonium bromide 21. Various aminyl radicals examined in this study were found to combine exclusively with the internal carbon of their double bond to give a five- (5a–5l) or six-membered ring (13). No product arising from the cyclization is obtained from N-methyl-1-phenylbut-3-enylamine (14).

Conformationally selective transannular cyclizations of humulene 9,10-epoxide. Synthesis of the two skeletally different cyclohumulanoids: dl-bicyclohumulenone and dl-africanol

Two cyclohumulanoids, dl-bicyclohumulenone (4) and dl-africanol (7 were synthesized through newly developed conformationally selective transannular cyclization of humulene 9,10-epoxide (2). The epoxide 2 was converted to a bicyclohumulenediol diacetate 3a in 70% yield by treatment with BF3·OEt2-Ac2O, while treatment of 2 with trimethylsilyl trifluoromethansulfonate gave an africen-10-ol (5a and 5b) in 80% yield. The two intermediates 3a and 5a furnished the natural products 4 and 7 in 30 and 8 % yield from 2 respectively.

Structure of antifungal and phytotoxic pigments produced by alternaria sps.

Abstract New antifungal hydroxyhydroperylenediones have been isolated from Alternaria sps. and their structures have been shown to be 1 and 2 .

Aminyl radical cyclization by means of anodic oxidation. Stereoselective synthesis of cis-1-methyl-2,5-disubstituted pyrrolidines

Abstract Neutral aminyl radicals generated by anodic oxidation of lithium alkenylamides 2 undergo a stereoselective cyclization to give cis -1-methyl-2,5-disubstituted pyrrolidines 4. Their cis stereochemistry was confirmed by a comparison with trans -1,2-dimethyl-5-phenylpyrrolidine, the structure of which was established by X-ray crystallographic analysis of its quarternary ammonium bromide 6.

Acetylpinnasterol and pinnasterol, ecdysone-like metabolites, from the marine red alga yamada

Abstract The structures of two sterols, isolated from the title alga and designated as acetylpinnasterol and pinnasterol, were determined on the basis of the X-ray crystallography. These metabolites are the first marine phytosterols with ecdysone-like structures and biological activity as moulting hormones.

Epoxydictymene, a new diterpene from the brown alga

Abstract Structure of epoxydictymene ( 1 ), a new tetracyclic diterpene from Dictyota dichotoma , has been determined mainly on the basis of X-ray analysis.

The absolute configuration of cycloeudesmol from the red alga Laurencia nipponica Yamada

Abstract The absolute configuration of cycloeudesmol, isolated from the red alga Laurencia nipponica Yamada and Chondria oppositiclada Dawson, is determined by the crystallographic study.

Structure of spironippol, a new sesquiterpene, from the red alga yamada

Abstract A new sesquiterpene, designated as spironippol, was isolated from the title alga. The structure, which was determined on the basis of the spectral data and X-ray crystallography, represents the biogenetic transition between chamigrane and perforane sesquiterpenes.