Takayuki Oritani

Microbiological degradation of (-)-geosmin

One of the musty odour components in drinking water, (-)-geosmin was microbiologically degraded with the backwash water collected from a biological filter pilot plant at Lake Biwa (Japan) and activated sludge obtained from Sendai City Sewerage Bureau; in this process the presence of ethanol was essential for acceleration of the reaction. Four biodegradation products were detected by gas chromatography, among which a dehydration product and an oxidation product were identified by mass spectroscopic comparison with unambiguously synthesized authentic samples.

Synthesis of (+)-Ambrein

Abstract Enantiomerically pure (+)-Ambrein was synthesized from (+)-drimane-8,11-diol prepared via lipase catalyzed kinetic resolution, and easily prepared (+)-γ-cyclogeraniol.

An efficient method for converting alcohols to azides with 2,4,4,6-tetrabromo-2,5-cyclohexadienone/PPh3/Zn(N3)2·2Py

Treatment of the salt generated from 2,4,4,6-tetrabromo-2,5-cyclohexadienone and PPh3 in a mixed solvent of CH3CNtoluene with primary and secondary alcohols in the presence of Zn(N3)2·2Py led to azides in excellent yields with inversion of configuration. Addition of hexamethylphosphorictriamide considerably accelerated the reaction.

Practical synthesis of Ambrox® from farnesyl acetate involving lipase catalyzed resolution

Abstract Enantiomerically pure Ambrox ® was synthesized from (−)-13,14,15,16-tetranor-8α,12-labdanediol, which was prepared by lipase catalyzed kinetic resolution of (±)-drimane-8,11-diol.

A mild and efficient method for converting alcohols and tetrahydropyranyl ethers to bromides with inversion of configuration

Bromotriphenylphosphonium salt 2, generated by adding 2,4,5,6-tetrabromo-2,5-cyclohexadienone (1) to triphenylphosphine in CH2Cl2 or CH3CN converted alcohols and tetrahydropyranyl ethers to the corresponding bromides in high yields.

Stereoselectivity in the biosynthetic conversion of xanthoxin into abscisic acid

All stereoisomers of xanthoxin (XAN) and abscisic aldehyde (ABA-aldehyde) were prepared from (R) and (S)-4-hydroxy-β-cyclogeraniol via asymmetric epoxidation. Their stomatal closure activities were measured on epidermal strips of Commelina communis L. Natural (S)-ABA-aldehyde showed strong activity comparable to that of (S)-abscisic acid (ABA). Natural (1′S, 2′R, 4′S)XAN and (1′S, 2′R, 4′R)-epi-XAN also induced stomatal closure at high concentrations. On the other hand, unnatural (1′R)-enantiomers of XAN, epi-XAN, and ABA-aldehyde were not effective. To further examine the Stereoselectivity on the biosynthetic pathway to ABA, deuterium-labeled substrates were prepared and fed to Lycopersicon esculentum Mill, under non-stressed or water-stressed conditions. Substantial incorporations into ABA were observed in the cases of natural (1′S, 2′R, 4′S)-XAN, (1′S, 2′R, 4′R)-epi-XAN and both enantiomers of ABA-aldehyde, leading to the following conclusions. The negligible effect of unnatural (1′R)-enantiomers of XAN, epi-XAN and ABA-aldehyde can be explained by their own biological inactivity and/or their conversion to inactive (R)-ABA. Even in the isolated epidermal strips, putative aldehyde oxidase activity is apparently sufficient to convert ABA-aldehyde to ABA while the activity of XAN dehydrogenase seems very weak. The stereochemistry of the 1′, 2′-epoxide is very important for the XAN-dehydrogenase while this enzyme is less selective regarding the 4′-hydrdxyl group of XAN and converts both (1′S, 2′R, 4′S)-XAN and (1′S, 2′R, 4′R)-epi-XAN to (S)-ABA-aldehyde. Abscisic aldehyde oxidase can nonstereoselectively convert both (S) and (R)-ABA-aldehyde to biologically active (S) and inactive (R)-ABA, respectively.

Synthesis and biological evaluation of 4-deacetoxy-1,7-dideoxy azetidine paclitaxel analogues.

Three novel 4-deacetoxy-1,7-dideoxy azetidine paclitaxel analogues were synthesized through a convenient route that employed hydroboration-amination and intramolecular S(N)2-type substitution reaction from a natural taxoid taxinine. All analogues have been tested for cytotoxicity against three human tumor cell lines. None of them showed remarkable cytotoxicity compared to paclitaxel against tested tumor cell lines.

Total synthesis of (15S, 16R, 19S, 20R, 34S)-diepomuricanin☆

An eleven-step reaction sequence starting from enantiomerically pure (−)-muricatacin (6) afforded the key intermediate 12, which was then converted to (15S, 16R, 19S, 20R, 34S)-diepomuricanin (1) via introduction of an acetylene unit and a coupling reaction with iodo lactone synthon 15.

Phenolic ferrier reaction and its application to the natural product synthesis

Abstract Aryl O -Δ 2 -glycosides were synthesized by Ferrier reaction. p -Methoxyphenyl group was oxidatively removed with Ag(DPAH) 2 .

Synthesis and biological evaluation of novel 9-functional heterocyclic coupled 7-deoxy-9-Dihydropaclitaxel analogue

Novel 9-functional heterocyclic coupled 7-deoxy-9-dihydropaclitaxel analogues 17 and 22-24 synthesized from a natural taxoid 5-cinnamoyltriacetyltaxicin-I (3) and their biological evaluation in tubulin assembly activity and cytotoxicity in vitro against several human tumor cell lines are first presented. The biologically tested results show that 17, 22 and 23 are inactive in tubulin assembly assay and have no more remarkable cytotoxicities against human tumor cell lines SK-OV3, WIDR and MCF-7, though 22 and 23 exhibit more potent cytotoxicity against human liver cancer and human esophagus cancer cell lines (BEL-7402 and ECa-109) than paclitaxel.