Yoshiro Yamagiwa

Syntheses of anacardic acids and ginkgoic acid

Abstract Syntheses of two anacardic acids [6-pentadecyl- and 6-(10-pentadecenyl) salicylic acid], inhibitors of prostaglandin synthetase and of the growth of certain insects, and ginkgoic acid via directive metallation is reported.

Synthesis of a straight chain analog of penaresidins, azetidine alkaloids from marine sponge Penares sp.

Abstract The straight-chain analog of penaresidins, azetidine alkaloids from the Okinawan marine sponge Penares sp., have been synthesized from D-xylose. The key step in the synthesis includes the biomimetic-type ring closure of phytosphingosines. The novel isomerization through an azabicylobutyl ion-pair is also described.

Inhibitory effects of cardols and related compounds on superoxide anion generation by xanthine oxidase

5-Pentadecatrienylresorcinol, isolated from cashew nuts and commonly known as cardol (C₁₅:₃), prevented the generation of superoxide radicals catalysed by xanthine oxidase without the inhibition of uric acid formation. The inhibition kinetics did not follow the Michelis-Menten equation, but instead followed the Hill equation. Cardol (C₁₀:₀) also inhibited superoxide anion generation, but resorcinol and cardol (C₅:₀) did not inhibit superoxide anion generation. The related compounds 3,5-dihydroxyphenyl alkanoates and alkyl 2,4-dihydroxybenzoates, had more than a C9 chain, cooperatively inhibited but alkyl 3,5-dihydroxybenzoates, regardless of their alkyl chain length, did not inhibit the superoxide anion generation. These results suggested that specific inhibitors for superoxide anion generation catalysed by xanthine oxidase consisted of an electron-rich resorcinol group and an alkyl chain having longer than C9 chain.

Synthesis of phosphonosphingoglycolipid found in marine snail turbo cornutus

Abstract The phosphonosphingoglycolipid (1) found in marine snail Turbo cornutus is synthesized from galactose as a chiral precursor via condensation of cerebroside (7) with protected phosphonic acid using DEC as the key step.

Synthesis of hepialone; principal component from male sex scales of hepialus californicus (lepidoptera)

Abstract Racemic and optically active hepialone, a new sex-pheromonal component produced by the male moth, Hepialus californicus Bvd., was synthesized and thus confirmed the structure of the pheromone as (2R)-2,3-dihydro-2-ethyl-6-methyl-4H-pyran-4-one (1).

UNIQUE TETRANUCLEAR COPPER(II) CLUSTER AND MONOMERIC IRON(II), (III) COMPLEXES WITH A TRIS(IMIDAZOLYL) CHELATING LIGAND

Copper(II) and iron(II, III) complexes of the tripodal ligand, tris(1-methyl-1 H -imidazol-2-yl)methanol (Htmim), have been synthesized and characterized by elemental analysis, 1 H NMR and IR spectroscopies, magnetic moment measurement and X-ray crystallography. The structure of the copper complex, [Cu 4 (tmim) 4 (CF 3 SO 3 ) 2 ](CF 3 SO 3 ) 2 ·2MeOH ( 1 ), can be regarded as a polyimidazole-linked tetranuclear cluster where each copper atom adopts a five-coordinate square-pyramidal geometry ligated by the tmim anion. The two iron complexes, [Fe II (Htmim) 2 ][Fe II Cl 4 ]·4MeOH ( 2 ) and [Fe III (Htmim) 2 ][Fe III Cl 4 ] 2 Cl ( 3 ), contain the isostructural [Fe(Htmim) 2 ] cation and tetrahedral [FeCl 4 ] − anion. While Htmim shows a normal tripodal tridentate mode in the iron complexes capping one face of an essentially octahedral coordination sphere, its deprotonated species exhibit an unusual non-tripodal tetradentate coordination with copper(II) ions. The observed magnetic moment at room temperature for 1 is 1.13 BM per Cu atom, consistent with antiferromagnetic coupling between the copper(II) atoms of the tetramer. Both 2 and 3 show magnetic properties consistent with low-spin electronic configurations of the cation and high-spin nature of the metal ion in the anion.

SRS-A antagonist pyranoquinolone alkaloids from East African Fagara plants and their synthesis

Three pyranoquinolone alkaloids isolated from two East African Fagara plants have been found to exhibit SRS-A antagonist action. Their synthesis has been accomplished, using a modified Coppolas method or a thermal cyclization followed by an electrocyclic ring closure.

Perkin communications. Synthesis of chiral long-chain α-hydroxy acids from L-ascorbic acid. Useful components for the synthesis of cerebrosides

Nucleophilic ring opening of chiral epoxy diols, derived from L-ascorbic acid, with 2-lithio-1,3-dithianes allowed preparation of long-chain (R)- and (S)-α-hydroxy acids of high optical purity.

A convenient stereoselective synthesis of D-erythro-C18-sphingosine from galactal

The highly efficient stereoselective synthesis of D-erythro-C18-sphingosine from 3,4,6-tribenzyloxygalactal via 4,6-tribenzyloxy-5-hydroxyhexenal is described.

Synthesis of 2,3-di-O-phytanyl-1-O-(α-D-glucopyranosyl)-sn-glycerol derivatives, analogues of polar lipids isolated from a halophilic bacterial strain

Abstract2,3-Di-O-phytanyl-1-O-glucopyranosylglycerol and polar derivatives of its 6′-glucose moiety have been synthesized. The target molecule contains the diphytanyl-sn-glycerol moiety which is α-linked to glucose. The key step in its synthesis involves the coupling of phytanyl bromide and isopropylidene threitol. We also demonstrated that the 6′-hydroxyl group of glycolipids can be functionalized without protection of the sugar moiety.