Tadao Kamikawa

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.

Sulfated glycoglycerolipid from Archaebacterium inhibits eukaryotic DNA polymerase α, β and retroviral reverse transcriptase and affects methyl methanesulfonate cytotoxicity

A sulfated glycoglycerolipid, 1‐O‐(6′‐sulfo‐α‐d‐glucopyranosyl)‐2,3‐di‐O‐phytanyl‐sn‐glycerol (KN‐208), a derivative of the polar lipid isolated from an archaebacterium, strongly inhibited DNA polymerase (pol) α and pol β in vitro among 5 eukaryotic DNA polymerases (α, β, γ, δ, and ϵ). It also inhibited Escherichia coli DNA polymerase I Klenow fragment (E. coli pol I) and human immunodeficiency virus reverse transcriptase (HIV RT). The mode of inhibition of these polymerases was competitive with the DNA template primer and was non‐competitive with the substrate dTTP. KN‐208 inhibited pol β most strongly, with a Ki value of 0.05 μM, 10‐fold lower than that for pol α (0.5 μM) and 60‐ or 140‐fold lower than that for HIV RT (3 μM) or for E. coli pol I (7 μM), respectively. The loss of sulfate on the 6′‐position of glucopyranoside of this compound completely abrogated inhibition. However, the hydrophilic part of KN‐208, glucose 6‐sulfate alone, showed no inhibition. Other sulfated compounds containing different hydrophobic structures, such as dodecyl sulfate and cholesterol sulfate, exhibited a much weaker inhibition. Our results suggest that the whole molecular structure of KN‐208 is required for inhibition. KN‐208 was shown to be modestly cytotoxic for the human leukemic cell line K562. Interestingly, a subcytotoxic dose of KN‐208 increased the sensitivity of the human leukemic cells to an alkylating agent, methyl methanesulfonate, while it did not potentiate the effects of ultraviolet light or of cisplatin. Int. J. Cancer 76:512–518, 1998.© 1998 Wiley‐Liss, Inc.

Total syntheses of O4,9-dimethyl stealthins A and C

O4,9-Dimethylstealthin A (11-amino-5-hydroxy-2-hydroxymethyl-4,9-dimethoxy-benzo[b]fluoren-10-one) and O4,9-dimethylstealthin C (11-amino-5-hydroxy-4,9-dimethoxy-2-methyl-benzo[b]fluoren-10-one), methylated derivatives of radical scavengers produced by Stereptomyces viridochromogenes, were synthesized using the Suzuki coupling reaction as a key step.

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.

THE STRUCTURE OF INFLEXIN

The structure of inflexin isolated from the leaves of Isodon inflexus has been determined as 1 by spectroscopic and chemical methods. Inflexin exhibits cytotoxicity, insect antifeedant and other bioactive properties.

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.

Total syntheses of O4,O9-dimethylstealthins A and C1

O 12 -Acetyl-O4,O9-dimethylstealthin A (2-acetoxymethyl-11-amino-5-hydroxy-4,9-dimethoxybenzo[b]fluoren-10-one and O4,O9-dimethylstealthin C (11-amino-5-hydroxy-4,9-dimethoxy-2-methylbenzo[b]fluoren-10-one), methylated derivatives of potent radical scavengers produced by Streptomyces viridochromogenes, have been synthesized using Suzuki coupling as a key step.