Comparative inhibition of tetrameric carbonyl reductase activity in pig heart cytosol by alkyl 4-pyridyl ketones.

CONTEXT AND OBJECTIVE: The present study is to elucidate the comparative inhibition of tetrameric carbonyl reductase (TCBR) activity by alkyl 4-pyridyl ketones, and to characterize its substrate-binding domain. MATERIALS AND METHODS: The inhibitory effects of alkyl 4-pyridyl ketones on the stereoselective reduction of 4-benzoylpyridine (4-BP) catalyzed by TCBR were examined in the cytosolic fraction of pig heart. RESULTS: Of alkyl 4-pyridyl ketones, 4-hexanoylpyridine, which has a straight-chain alkyl group of five carbon atoms, inhibited most potently TCBR activity and was a competitive inhibitor. Furthermore, cyclohexyl pentyl ketone, which is substituted by cyclohexyl group instead of phenyl group of hexanophenone, had much lower ability to be reduced than hexanophenone. DISCUSSION AND CONCLUSION: These results suggest that in addition to a hydrophobic cleft corresponding to a straight-chain alkyl group of five carbon atoms, a hydrophobic pocket with affinity for an aromatic group is located in the substrate-binding domain of TCBR.

Synthesis of γ- and δ-lactone natural products by employing a trans-cis isomerization/lactonization strategy.

Alkaline hydrolysis of 4-hydroxy- or/and 5-hydroxy-(2E)-alkenoate followed by acid treatment gave the corresponding (2E)-alkenoic acids which were subjected to lactone formation reaction without further purification. The crude acids were treated with 2,4,6-trichlorobenzoyl chloride in pyridine to afford γ-lactone or δ-lactone, respectively, accompanied by trans-cis isomerization. By this procedure, (±)-(4,5)-trans-5-benzyloxy-2-hexen-4-olide (90% overall yield), (S)-5-hydroxy-2-penten-4-olide (86% overall yield), (4S,5R)-5-hydroxy-2-hexen-4-olide (86% overall yield), (4R,5S)-5-hydroxy-2-hexen-4-olide (82% overall yield), (S)-parasorbic acid (58% overall yield) and natural product, (5R,7S)-7-hydroxy-2-octen-5-olide (euscapholide: 20% overall yield) were synthesized.

The asymmetric syntheses of methyl D-digitoxoside, L-oleandrose and L-cymarose from methyl sorbate, an achiral precursor.

The addition of 4 eq of chloral to osmundalactone (4S,5R)-4 gave quantitative formation of the hemiacetal derivative (4S,5R)-8, which was treated with methane sulfonic acid to afford the intramolecular Micheal addition product (+)-(3S,4S,5R)-9 possessing a 3,4-cis-dihydroxy-δ-lactone in 78% overall yield from (4S,5R)-4. The obtained (+)-(3S,4S,5R)-9 was subsequently converted to methyl D-digitoxoside (pyranoside) (12) in 13% overall yield and methyl D-digitoxoside (furanoside) (12) in 20% overall yield. The reaction of benzyl-osmundalactone (4R,5S)-3 and MeOH in the presence of Amberlyst A-26 as a basic catalyst gave 3,4-trans-δ-lactone (-)-(3S,4R,5S)-20 in 28% yield and 3,4-cis-δ-lactone (-)-(3R,4R,5S)-21 in 45% yield. Dibal-H reduction of (-)-(3S,4R,5S)-20 followed by catalytic hydrogenation gave L-oleandrose (6) in 86% overall yield, while Dibal-H reduction of (-)-(3R,4R,5S)-21 followed by catalytic hydrogenation provided L-cymarose (7) in 85% overall yield.

Acid-promoted rearrangement of drimane type epoxy compounds and their application in natural product synthesis.

The reactions of (±)-α-epoxy drimenol (4) and (±)-α-epoxy drimenyl cyanide (6) with acids (proton acid or Lewis acid) selectively gave the rearranged aldehyde (±)-13 and (±)-15 having the hydroindane skeleton, respectively, while the reactions of (±)-4 and (±)-6 with Dibal-H selectively afforded the allyl alcohol (±)-14 and (±)-16, respectively. The reactions of (8aR)-6 and (8aS)-6 with Dibal-H were applied for the determination of the absolute structure of natural 7ß-acetoxy-ent-labda-8(17),13(14)E-dien-15-ol (18). The reaction of (±)-α-epoxy bicyclofarnesol (5) and (8aS)-5 with proton acid selectively provided the rearranged ketol (±)- and (8aS)-31 having the hydroindane skeleton, respectively. The optically active (8aS)-31 was converted to the natural (9S)-austrodoric acid (33).

[Natural products syntheses based on the biotransformation using biocatalyst].

This review summarizes the chemoenzymatic synthesis of the biologically active natural products based on a combination of chemical diastereoselectivity and enzymatic enantioselectivity using biocatalyst. Asymmetric reduction of 2-methyl-3-keto ester with yeast gave the optically active syn-2-methyl-3-hydroxy ester, which was converted to natural product such as (-)-oudemansin B. Asymmetric hydrolysis of 3-acetoxy-2-methy esters possessing syn- or anti-structure afforded the optically active 3-hydroxy-2-methyl esters and 3-acetoxy-2-methy esters corresponding to the starting material. One of these optically active 3-hydroxy-2-methyl esters was converted to aglycone of macrolide, venturicidins A and B possessing 10 chiral centers. Both primary alcohols possessing a chiral center at ß-position of hydroxyl group and secondary alcohols were subjected to the lipase-assisted acylation in the presence of acyl donor to afford the optically active esters and the optically active alcohols corresponding to the starting material. These optically active compounds were converted to the biologically active natural products such as bisabolane type sesquiterpenes, decaline type diterpenes or triterpenes, nikkomycin B, (+)-asperlin, (-)-chuangxinmycin, (-)-indolmycin, cystothiazoles melithiazols, myxothiazols and piericidins possessing antifungal and cytotoxicic activities, inhibition of NADH oxidation, etc. Reaction of primary alcohol and glucose using immobilized ß-glucosidase gave alkyl ß-glucosides in high yield. Pentaacetate of allyl ß-glucoside was subjected to Mizoroki-Heck type reaction with phenylboronic acid derivatives to give phenylpropenoid ß-D-glucopyranosid congeners.

Nucleophilic addition to 2,3-disubstituted butanal derivatives and their application to natural product synthesis.

The reaction of 2,3-anti-2-tert-butyldimethylsiloxy-3-substituted butanal derivative [anti-B, (±)-10 and (±)-16] derived from trans-(2,3)-epoxy butanoate (1) with carbon nucleophiles [α-furyl anion, acetate anion, and indium (In)-assisted allyl anion] has been investigated to give selectively the anti-, anti-adduct D. This anti-stereoselection could be explained by the Felkin-Anh transition state model. Thus obtained anti-, anti-adducts (±)-17 and (±)-38 were formally converted to natural products, (±)-asperlin (2) and (±)-olivose (4), respectively. The major anti-, anti-adduct (±)-26 was converted to (±)-digitoxose (3), while the minor anti-, syn-adduct (±)-27 was also converted to (±)-olivose (4). The reaction of (±)-10 with tert-butyl acetate anion gave predominantly afforded the anti-, anti-adduct (±)-23, which was converted to (±)-1,5-dideoxyhexitol (25). Alternately, the reaction of 2,3-syn-2-tert-butyldimethylsiloxy-3-p-methoxyphenoxy butanal derivative [syn-B, (±)-14] derived from trans-(2,3)-epoxy butanoate (1) with carbon nucleophile (In-assisted allyl anion) afforded a ca. 1 : 1 mixture of the syn-, anti-adduct E [(±)-32 or (±)-34] and syn-, syn-adduct F [(±)-33 or (±)-35]. After separation of this mixture, (±)-34 and (±)-35 were separately converted to (±)-oliose (5) and (±)-boivinose (6), respectively.

Synthesis of ß-methoxyacrylate natural products based on box-Pd(II)-catalyzed intermolecular methoxycarbonylation of alkynoles.

Bis(oxazoline)-palladium(II) catalyzed carbonylation of homopropargyl alcohols afforded acyclic methoxyacrylate 2 and 6-membered lactone 3a-k in good combined yield. In the case of propargyl alcohols, 5-membered lactones 3p, 3q, 16 were obtained in moderate yields. The one-pot synthesis of kawa lactones 3a, 3r, 3s and formal synthesis of dihydroxycystothiazole A and dihydroxycystothiazole C are presented. To elucidate the stereochemistry of (+)-annularin G and (-)-annularin H, the first asymmetric syntheses of these natural products were achieved.

First syntheses of (-)-tauranin and antibiotic (-)-BE-40644 based on lipase-catalyzed optical resolution of albicanol.

First syntheses of sesquiterpene quinones (-)-tauranin and (-)-BE-40644 which exhibited strong cytotoxicity against several cancer cell lines, were achieved from (8aS)-albicanol obtained by enzymatic optical resolution. By comparison of the sign of specific rotation between synthetic (12bS)-BE-40644 and natural (-)-BE-40644, the absolute configurations of natural (-)-BE-40644 were determined to be 4aS, 6aS, 12aR, 12bS.

Intermolecular methoxycarbonylation of terminal alkynes catalyzed by palladium(II) bis(oxazoline) complexes.

Boxing clever: Direct conversion of a terminal alkyne group into a beta-methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid-sensitive glycosidic bonds are not affected under the reaction conditions. The one-pot synthesis of (+/-)-dihydrokawain from the homopropargyl alcohol is also achieved. tfa = trifluoroacetate.

Conversion of optically active hydrindanone to (+)-bakkenolide-A.

A total synthesis of (+)-bakkenolide-A was carried out via the key intermediate 4, which was prepared based on an asymmetric cyclization-carbonylation reaction established in our laboratory. Diastereoselective construction of the spirolactone moiety was achieved using Mitsuhashi's protocol as a key step.

meso-Phbox-Pd(II) catalyzed tandem carbonylative cyclization of 1-ethynyl-1-propargyl acetate.

Palladium(II) catalyzed carbonylation of 1-ethynyl-1-propargyl acetate is described; in the absence of the bisoxazoline (box) ligand, the second triple bond did not react, affording cyclic orthoesters and . The use of meso-Phbox-Pd(ii) strikingly changed the course of the reaction, yielding bicyclic lactone by tandem carbonylative cyclization as a result of insertion of the second triple bond.

Concise syntheses of coronarin A, coronarin E, austrochaparol and pacovatinin A.

Total syntheses of (+)-coronarin A (1), (+)-coronarin E (2), (+)-austrochaparol (3) and (+)-pacovatinin A (4) were achieved from the synthetic (+)-albicanyl acetate (6). Dess-Martin oxidation of (+)-albicanol (5) derived from the chemoenzymatic product (6) gave an aldehyde (7), which was subjected to Julia one-pot olefination using beta-furylmethyl-heteroaromatic sulfones (8 or 9 ) gave (+)-trans coronarin E (2) and (+)-cis coronarin E (12) with high cis-selectivity. The synthesis of (+)-coronarin A (1) from (+)-trans coronarin E (2) was achiev-ed, while (+)-cis coronarin E (12) was converted to the natural products (+)-(5S,9S,10S)-15,16-epoxy-8(17),13(16),14-labdatriene (13) and (+)-austrochaparol (3). By the asymmetric synthesis of (+)-3, the absolute structure of (+)-3 was determined to be 5S, 7R, 9R, 10S configurations. Homologation of (+)-albicanol (5) followed by allylic oxidation gave (7 alpha)-hydroxy nitrile (17), which was finally converted to the natural (+)-pacovatinin A (4) in 8 steps from (+)-albicanol (5).

Process development and large-scale synthesis of NK1 antagonist.

A scaleable synthetic route is described to obtain 2-(4-acetylpiperadin-1-yl)-6-[3,5-bis(trifluoromethyl)phenylmethyl]-4-(2-methylphenyl)-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,5]oxazocin-5-one (1, KRP-103) as a neurokinin (NK)(1) antagonist. The key step in the synthesis is the intramolecular cyclization of N-[3,5-bis(trifluoromethyl)phenylmethyl]-N-(3-hydroxypropyl)-4-chloro-6-(2-methylphenyl)-2-methylthiopyrimidine-5-carboxamide (15) which was obtained by amide formation between 4-(2-methylphenyl)-2-methylthio-6-oxo-1,6-dihydropyrimidine-5-carboxylic acid (8) and 3-[3,5-bis(trifluoromethyl)phenylmethylamino]-1-propanol (3). Treatment of 15 with 1,8-diazabicyclo[5,4,0]undec-7-ene provided 6-[3,5-bis(trifluoromethyl)phenylmethyl]-4-(2-methylphenyl)-2-methylthio-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,5]oxazocin-5-one (6). This intermediate (6) is transformed into the candidate compound (1) by two steps; oxidation, and substitution reaction of the resultant sulfone (7) with 1-acetylpiperazine. This synthetic method is free of chromatographic purification and is amenable to large scale synthesis.

Chemoenzymatic synthesis of (+)-alpha-polypodatetraene and methyl (5R,10R,13R)-labda-8-en-15-oate.

The reported enzymatic resolution products {acetate of (1S,4aS,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal} (8aS)-5 (>99% ee)] and [(1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-4 (98% ee) were converted to (+)-alpha-polypodatetraene (1) and methyl (5R,10R,13R)-labda-8-en-15-oate (2), respectively. For the synthesis of (5R,10R,13R)-2, chiral isoprene congener (3S)-26 corresponding to the right part of 2 was synthesized based on the lipase-assisted resolution of (+/-)-2-methyl-3- (p-methoxyphenyl)propanol (17).

Concise syntheses of cystothiazoles A, C, D, and melithiazol B.

A convergent synthesis of cystothiazoles C 1 and D 3 was achieved based on Julia coupling between the functionalized aldehyde 5b, corresponding to left half of the final molecule, and aryl sulfone 6 or 7, bearing a bithiazole moiety, corresponding to right half. Methylation of 1 and 3 gave cystothiazole A 2 and melithiazol B 4, respectively. The overall yield (5 steps from (2R,3S)-3-methylpent-4-yne-1,2-diol 10; 57%) of 5b via the present route was improved in comparison to that of the previously reported functionalized aldehyde 5a (7 steps from 10; 13%). By applying the modified Julia coupling method, selectivity (6E/6Z=20 : 1-26 : 1) toward the (6E)-form of the coupled products (15 or 19) against the corresponding (6Z)-form was improved in comparison to the Wittig method (6E/6Z=4 : 1-6.9 : 1).

(R)-ACX, a pancreatic beta-cell selective sulfonylurea, does not aggravate myocardial ischemia-reperfusion damage.

The organ selectivity and the effect on myocardial ischemia-reperfusion injury of (R)-acetoxyhexamide ((R)-ACX), a novel sulfonylurea, were examined. (R)-ACX, as well as glibenclamide, concentration-dependently stimulated insulin release from INS-1 cell, a cell line derived from pancreatic beta-cells. The potency of (R)-ACX was about 1/10 of that of glibenclamide. In isolated guinea pig ventricular myocardial tissue, glibenclamide concentration-dependently inhibited the action potential shortening by NIP-121, an ATP-sensitive potassium channel opener, but (R)-ACX showed only slight inhibition. In isolated rat aortic rings contracted with norepinephrine, glibenclamide concentration-dependently inhibited the relaxation by NIP-121, while (R)-ACX showed only slight inhibition. In coronary-perfused guinea pig ventricular preparations, glibenclamide reduced the recovery of contractile force after ischemia-reperfusion, while (R)-ACX did not. In conclusion, (R)-ACX is a beta-cell selective sulfonylurea which, unlike glibenclamide, does not aggravate cardiac ischemia-reperfusion damage.

Control of chemoselectivity of microbial reaction with resin adsorbent: enhancement of Baeyer-Villiger oxidation over reduction.

Amberlite XAD-7, a hydrophobic polymer, was used to change microbial reaction of ketones from reduction to Baeyer-Villiger (BV) oxidation. Thus, D. magnusii NBRC 4600 and G. reessii NBRC 1112 could catalyze the BV reaction of ketones in the presence of the polymer while reduction of the substrates proceeded, and BV oxidation was scarcely found in the absence of the polymer.

Synthesis of (R)-curcumene and (R)-xanthorrizol based on 1,2-Aryl migration via phenonium ion.

Solvolysis reaction of methyl (4S,5S)-4-(4'-methoxyphenyl)-5-tosyloxy-2(E)-hexenoate 5 in water-saturated MeNO(2) gave the 1,2-migration product, (4S,5S)-5-hydroxy-4-(4'-methoxyphenyl)-2-(E)-hexenoate 6 (55% yield), which was converted to methyl (R)-(4'-methylphenyl)hexanoate 11 in 25% overall yield (5 steps). Treatment of (R)-11 with MeLi gave tertiary alcohol congener 12, which was subjected to dehydration to afford (R)-(-)-curcumene 1. An introduction of hydroxyl group at meta-position of the aromatic ring in (R)-11 was achieved based on consecutive treatment [1) selective iodination, 2) conversion of aryl iodide to aryl boronate, 3) conversion of aryl boronate to phenol]. Thus obtained phenol (R)-16 was treated with MeLi to give tertiary alcohol congener 17, which was subjected to dehydration to afford (R)-(-)-xanthorrizol 2.

Incoherent quasielastic neutron scattering study on the polymorphism of tristearin: dynamical properties of hydrocarbon chains.

Dynamical properties of acyl chains in the three polymorphic phases alpha, beta', and beta of tristearin [C(3)H(5)(OCOC(17)H(35))3] have been studied by means of incoherent quasielastic neutron scattering (IQNS) using selectively deuterated samples. The mean square displacement of hydrogen atoms, , was estimated from the scattering vector Q dependence of the elastic scattering component under the harmonic approximation. It was shown that the temperature dependence of was significantly different between the three phases. There was no marked difference in between these phases up to 193 K, and the value increased linearly with temperature. Although the beta phase remained linear up to 293 K, the alpha and beta' phases started to show a nonlinear increase around 200 K, suggesting an anharmonic nature of molecular motions. The alpha phase exhibited the most conspicuous temperature dependence. These characteristics were ascribable to the difference in the lateral packing of acyl chains. Compared with the beta phase which has a tightly packed T// subcell, the beta' and alpha phases have looser O perpendicular and H subcells, respectively. The molecular motion in the alpha phase was analyzed using the model of uniaxial rotational diffusion in a onefold cosine potential. It has been clarified that the rotational fluctuation about the chain axis in the alpha phase is rather restricted compared with that in the rotator phase of n-alkanes.

Synthesis of the metabolites of 4-(2-methyl-1H-imidazol-1-yl)-2,2-diphenylbutanamide (KRP-197/ONO-8025).

We synthesized the six presumed metabolites (2--7) of 4-(2-methyl-1H-imidazol-1-yl)-2,2-diphenylbutanamide [KRP-197/ONO-8025, 1], a urinary incontinence therapeutic agent, in order to confirm the structures of the metabolites. Metabolite (2) was synthesized via glucuronidaion of compound (1) and methyl 2,3,4-tri-O-benzoyl-1-methanesulfonyl-alpha-D-glucopyranuronate. Metabolite (3) was synthesized via 3-(tert-butoxycarbonyl)-2-methyl-1,3-imidazolidine-4,5-dione. Metabolites (4--7) were synthesized via 4-amino-2-diphenylbutanamide, respectively. The structures of the metabolites (2--7) in humans were identified by means of synthesis of the authentic compounds.