Takehisa Ohashi

Diastereoselective catalytic asymmetric nitroaldol reaction utilizing rare earth-Li-(R)-BINOL complex. A highly efficient synthesis of norstatine

Abstract Rare earth-Li-BINOL complexes were used to catalyze nitroaldol reactions of optically active α-amino-aldehydes with nitromethane in a highly diastereoselective manner. A typical adduct, (2S, 3S)-3-phthaloylamino-2-hydroxy-1-nitro-4-phenylbutane was conveniently converted to (2S, 3S)-3-amino-2-hydroxy-4-phenylbutanoic acid (erythro-AHPA ; phenylnorstatine), a component of the HIV protease inhibitor KNI-227 and KNI-272.

Effect of a new rifamycin derivative, rifalazil, on liver microsomal enzyme induction in rat and dog

1. The effect of a new rifamycin derivative, rifalazil (KRM-1648), on liver microsomal enzyme induction was studied in rat and dog with repeated oral administration of the compound. Relative liver weight, cytochrome b5 and P450 contents, enzyme activities of NADPH-cytochrome c reductase, aniline hydroxylase, p-nitroanisole O-demethylase, aminopyrine N-demethylase, and erythromycin N-demethylase were measured. 2. In rat, rifalazil treatment at 300 mg/kg/day for 10 days increased cytochrome b5 content but it did not affect liver weight, P450 content or enzyme activities. In contrast, rifampicin and rifabutin increased relative liver weights, cytochrome contents and enzyme activities under similar conditions. 3. In dog, rifalazil did not affect any parameters at 30 or 300 mg/kg/day for 13 weeks. 4. These findings indicate that rifalazil is not an enzyme inducer in rat and dog. This property differs from other rifamycin derivatives such as rifampicin and rifabutin.

High-yield Production of Optically Active 1, 2-Diols from the Corresponding Racemates by Microbial Stereoinversion

A novel method for producing optically active 1,2-diols by microbial Stereoinversion was developed. It was found that some microorganisms could convert only (R)-1,2-pentanediol in the racemate to the (S)-enantiomer. Candida parapsilosis produced 27.9 g/l of (S)-1,2-pentanediol from 30 g/l of the racemate in 24 hr of reaction (molar yield 93%, enantiomeric excess 100%). This Stereoinversion proceeded via oxidation of (R)-1,2-pentanediol to 1-hydroxy-2-pentanone by an NAD+-linked (R)-specific alcohol dehydrogenase and reduction of 1-hydroxy-2-pentanone to (S)-1,2-pentanediol by an NADPH-linked (S)-specific 2-keto-1-alcohol reductase. This microbial stereo-inversion was applicable to ten 1,2-diols. Optically active 1,2-diols prepared by the reaction had the same configuration at the chiral center.

A practical chemoenzymatic synthesis of a key intermediate of antifungal agents

Abstract A novel synthesis of an azole antifungal building block, the optically active diol, is described. The key step involves an enantioselective hydrolysis of a prochiral diester by a lipase.

In vitro metabolism of a rifamycin derivative by animal and human liver microsomes, whole blood and expressed human CYP3A isoform.

1. In vitro metabolism of a rifamycin derivative, benzoxazinorifamycin KRM-1648, was studied using mouse, rat, guinea pig, dog, monkey and human liver microsomes. 30-Hydroxy-KRM-1648 (M2) was produced in mouse, dog, monkey and human microsomes. 25-Deacetyl-KRM-1648 (M1) was produced in dog and human microsomes, but not in mouse or monkey microsomes. Neither M1 nor M2 was detected in rat or guinea pig microsomes. 2. In dog and human liver microsomes the formation of M2 was dependent on NADPH, but the formation of M1 was not. 3. In vitro metabolism of the parent compound was studied in whole blood in some species. Only M1 was detected in mouse and rat blood, and not in dog and human blood. 4. These findings demonstrated that the metabolite pattern in dog resembled that in man, and suggested that the 30-hydroxylation of KRM-1648 was mediated by cytochrome P450, but that the 25-deacetylation was not. 5. Among the ten recombinant human P450 isoforms used, only the cell lysates including CYP3A3 and CYP3A4 catalysed the M2 formation from KRM-1648.

A dimeric form of soluble recombinant sheep LFA-3(CD58) inhibits human T-cell proliferation by generating regulatory T cells.

We recently observed that the soluble recombinant from of sheep LFA-3, termed sLFA-3 is biologically active as determined by E-rosette inhibition and inhibition of human T-cell proliferation in response to the recall antigen. In the present study, we examined the immunosuppressive properties of a derivative of sLFA-3, a dimeric form of the first domain (D1) of sLFA-3, named sD1Hcys dimer which was made by oxidative binding of the two D1 molecules through disulfide bonds formed between the SH side chains of a cysteine which was added to the C-terminal of the D1 domain. By investigating the suppressive properties of the sD1Hcys dimer, we obtained evidence that antigen-stimulated T-cell proliferation was inhibited by the suppressor T cell, mainly CD4 + CD45RA - CD45RO + and CD8 + CD45RA - CD45RO + T cells, generated by incubating PBLs with a low dose (0.5 microgram/ml) of sD1Hcys dimer in the presence of a low dose of IL-2 and GM-CSF. Flow cytometric analysis showed that the expression of some surface molecules on T cells were modulated by a high dose (5 micrograms/ml) of sD1Hcys dimer such as downregulation of CD3 and upregulation of IL-2R, but were not modulated by a low dose (0.5 microgram/ml) of the sD1Hcys dimer. These findings suggest that the sD1Hcys dimer exerts its suppressive effects on the antigen-induced proliferation assay by generating suppressor T cells. The sD1Hcys dimer might therefore have potential as an immunotherapeutic agent to inhibit and/or anergize antigen-specific T-cell responses.