Yoshiki Hirose

Enzyme-catalyzed asymmetric acylation and hydrolysis of cis-2,5-disubstituted tetrahydrofuran derivatives: Contribution to development of models for reactions catalyzed by porcine liver esterase and porcine pancreatic lipase

Abstract Pig liver esterase, lipase from porcine pancreas, lipase from Pseudomonas sp. (lipase YS), and lipase from Candida cylindracea catalyzed hydrolyses of the cis -diacetate 1 and the trans -diacetate (±)- 4 to give the cis -monoacetate 3 and the trans -monoacetate 6 in optically active forms, respectively. Lipase YS-catalyzed acylations of the cis -diol 2 and the trans -diol (±)- 5 with an acylating agent in cyclohexane yielded (−)- 3 and (−)- 6 , respectively. The group adjacent to the R stereogenic center preferentially reacted in lipase YS-catalyzed hydrolyses of 1 and (±)- 4 and acylations of 2 and (±)- 5 , and the enantioselectivities are rationalized by our rule recently proposed for lipase YS.

(C/sub 5/Me/sub 5/)/sub 2/UCL-THF oxidative-addition reactions. 2. A kinetic and mechanistic study

Results of studies of the kinetics of the mechanisms of the one-electron U(III) to U(IV) organoactinide oxidative addition in the reaction of (C/sub 5/Me/sub 5/)/sub 2/UC1 THF with alkyl halides (RX) are presented. An atom-abstraction RX oxidative-addition mechanism to (C/sub 5/Me/sub 5/)/sub 2/ UC1 is indicated. The rate of the reaction in benzene was determined to be 10/sup 4/-10/sup 7/ times faster than any known isolable transition-metal system reacting by an atom-abstraction mechanism. The relative reaction rates of the (C/sub 5/Me/sub 5/)/sub 2/UC1 and (C/sub 5/Me/sub 5/)/sub 2/UC1 THF with alkyl halides were determined to be 20:0, and it is suggested that this difference in reactivity reflects the difference in the degree of coordinative unsaturation and thus the availability of an inner sphere pathway for the 7- and 8- coordinate U(III) species. (BLM)

Microbial stereo-differentiating reduction of carbonyl compounds; proposed quadrant rule

The stereochemistry of the alcohols obtained from microbial reduction (Curvularia lunata and Rhodotorula rubra) of the cyclic ketones (1)–(8) with a wide variation in molecular framework has led to the formulation of a quadrant rule which provides information on the absolute configuration of the substrate ketone.

(C5Me5)2UCl·tetrahydrofuran. Oxidative-addition and related reactions

The first examples of organoactinide oxidative-addition of alkyl halides are reported, reactions which proceed at unprecedented rates; the results presented include the stoicheiometries of these reactions, the new complexes (C5Me5)2UX2, (C5Me5)2UX(Y), and (C5Me5)2- UY(R)(X,Y = Br, I), the series of halide exchange equilibria by which these new complexes are formed, determination of the appropriate equilibrium constants to ± 10% independent syntheses for these new complexes, and evidence for a previously unknown type of UIII to UIV redox-halide exchange equilibrium and its equilibrium constant.

Horse liver alcohol dehydrogenase-catalyzed enantioselective reduction of cyclic ketones: The effect of the hydrophobic side chain of the substrate on the stereoselectivity of the reaction

Abstract Horse liver alcohol dehydrogenase (HLADH)-catalyzed enantioselective reductions of alkyl 3-oxocyclopentanecarboxylates, endo -5-acyloxybicyclo[2.2.1]heptan-2-ones and exo -5-acyloxybicyclo[2.2.1]heptan-2-ones gave the corresponding homochiral alcohols and ketones and the interaction between the hydrophobic side chain of the substrate and the hydrophobic zone in the active site played an important role in the specificity of the reduction. The stereoselectivities of the reactions were interpreted on the basis of the cubic space section model and a new rule, which contributes to development of a specificity analysis on the basis of the model, is introduced.

Pig liver alcohol dehydrogenase catalysed stereoselective reduction of cage-shaped ketones. Preparation of axially chiral (–)-(R)-adamantane-2,6-diol with high enantiomeric purity

In a study of the stereoselective reductions of various cage-shaped ketones catalysed by pig liver alcohol dehydrogenase (PLADH), a typical axially chiral diol, (–)-(R)-adamantane-2,6-diol 12a with high enantiomeric purity was prepared by asymmetric reduction of keto ester 11d; based on this a new, remarkable function of the active site of the enzyme, which serves to enhance the stereoselectivity of the reaction is suggested.

Enzymatic hydrolysis of 2,6-diacetoxybicyclo[3.3.1]nonane and 2,6-diacetoxy-3,3,7,7-tetramethylbicyclo[3.3.1]nonane; a facile synthesis of the optically active chiral subunit for crown ethers

Hydrolysis of 2,6-diacetoxybicyclo[3.3.1]nonane (5) using lipase from Candida cylindracea gave (+)-(1S,2R,5S,6R)-(4)[81% enantiomeric excess (e.e.)] and (–)-(1R,2S,5R,6S)-(5)[95% e.e.], and pig liver esterase-catalysed hydrolysis of 2,6-diacetoxy-3,3,7,7-tetramethylbicyclo[3.3.1]nonane (9) gave (–)-(1S,2R,5S,6R)-(7)(96% e.e.) and (+)-(1R,2S,5R,6S)-(9)(86% e.e.); the enantiomer recognition behaviour of the crown ethers (–)-(11) and (+)-(12) prepared from (–)-(3) and (+)-(7), respectively, has been examined.