Amano

Acetylsucrose [63648-81-7] has been prepared in 40% yield by direct acetylation of sucrose using acetic anhydride in pyridine at 40° C (36). The 6-ester has subsequently been obtained in greater than 90% yield, by way of 4,6-cycHc orthoacetate. Other selective methods for the 6-acylated derivatives include the use of alkyl tin reagents such as dibutyl tin oxide (37) and of dibutyl stannolane derivatives (38). Selective acetylation of sucrose by an enzymic process has also been described. Treatment of sucrose with isopropenyl acetate in pyridine in the presence of Lipase P Amano gave, after chromatography, 6-0-acetylsucrose (33%) and 4/6-di-O-acetylsucrose (8%). The latter compound has been obtained in 47% yield by the prolonged treatment (39). 

Optically Active Acids and Esters. Enantioselective hydrolysis of esters of simple alcohols is a common method for the production of pure enantiomers of esters or the corresponding acids. Several representative examples are summarized ia Table 4. Lipases, esterases, and proteases accept a wide variety of esters and convert them to the corresponding acids, often ia a highly enantioselective manner. For example, the hydrolysis of (R)-methyl hydratropate [34083-55-1] (40) catalyzed by Hpase P from Amano results ia the corresponding acid ia 50% yield and 95% ee (56). Various substituents on the a-carbon (41—44) are readily tolerated by both Upases and proteases without reduction ia selectivity (57—60). The enantioselectivity of many Upases is not significantly affected by changes ia the alcohol component. As a result, activated esters may be used as a means of enhancing the reaction rate. 

Both saturated (50) and unsaturated derivatives (51) are easily accepted by lipases and esterases. Lipase P from Amano resolves azide (52) or naphthyl (53) derivatives with good yields and excellent selectivity. PPL-catalyzed resolution of glycidyl esters (54) is of great synthetic utiUty because it provides an alternative to the Sharpless epoxidation route for the synthesis of P-blockers. The optical purity of glycidyl esters strongly depends on the stmcture of the acyl moiety the hydrolysis of propyl and butyl derivatives of epoxy alcohols results ia esters with ee > 95% (30). 

Cychc alcohols are excellent targets for enantioselective enzymatic acylations. For example, acylation of (65) with vinyl acetate catalyzed by Hpase SAM-II gives the (R),(3)-ester with 95% ee (81). Similarly (66), which is a precursor for seratonin uptake inhibitor, is resolved in a high yield and selectivity with Amano Hpase P (82). The prostaglandin synthon (67) is resolved by the same method into the optically pure alcohol in 35% yield (83). 

Alusuisse Lonza Group (Algroup) Ltd., 147 ALZA Corporation, 216 Amano Enzyme Inc., 180 Amantech Chemicals Pvt. Ltd., 168 Amber Chemical Company, 206 AMBUSH , permethrin, 12 AMCOL International Corporation, 216 Amerada-Hess Corporation, 216... 

Lipase Fp from Amano, vinyl acetate, 4 h, 90% yield. This method can also be used for the selective introduction of other esters, such as the methoxyacetyl, phenoxyacetyl, and phenylacetyl groups, in excellent yield. 

In contrast to oxoesters, the a-protons of thioesters are sufficiently acidic to permit continuous racemization of the substrate by base-catalyzed deprotonation at the a-carbon. Drueckhammer et al. first demonstrated the feasibility of this approach by performing DKR of a propionate thioester bearing a phenylthiogroup, which also contributes to the acidity of the a-proton (Figure 4.14) [39a]. The enzymatic hydrolysis of the thioester was coupled with a racemization catalyzed by trioctylamine. Owing to the insolubility of the substrate and base in water, they employed a biphasic system (toluene/H2O). Using P. cepacia (Amano PS-30) as the enzyme and a catalytic amount of trioctylamine, they obtained a quantitative yield of the corresponding... 

In 1992, Oda et al. reported a one-pot synthesis of optically active cyanohydrin acetates from aldehydes, which were converted to the corresponding racemic cyanohydrins through transhydrocyanation with acetone cyanohydrin, catalyzed by a a strongly basic anion-exchange resin [46]. The racemic cyanohydrins were acetylated by a lipase from P. cepacia (Amano) with isopropenyl acetate as the acyl donor. The reversible nature of the base-catalyzed transhydrocyanation enabled continuous racemization of the unreacted cyanohydrins, thereby effecting a total conversion (Figure 4.21). 

Ema M, Kurosaka R, Amano H, Ogawa Y (1995) Comparative developmental toxicity of butyltin trichloride, dibutyitin dichloride and tributyitin chloride in rats. Journal of Applied Toxicology, 15(4) 297-302. 

JOC2763 J. Ichikawa, M. Kobayashi, Y. Noda. N. Ytdcota, K. Amano, T. Minami, J. Org. Chem. 

Imamoto T, Hirose K, Amano H (1996) Main Group Chem. 1 331 Matsukawa S, Sugama H, Imamoto T (2000) Tetrahedron Lett 41 6461 Kyba EP, Liu S-T, Harris RL (1983) Organometallics 2 1877... 

Recently, an interesting example of the enzymatic kinetic resolution of a-acetoxyamide 8 was demonstrated using native wheat germ lipase and immobilized lipase PS (AMANO) (Scheme 5.6). 

PSL, AMANO) has been found to catalyze the Markovnikov-type addition of thiols to vinyl esters (Scheme 5.23) [114] and acylases aminoacylase [115], penicillin G acylase [116], and acylase from AspergiUus oryzae [117], the same kind of addition of various nitrogen nucleophiles. Unfortunately, most additions described above are nonstereoselective. 

Sato F, Wachi H, Starcher BC, Murata H, Amano S, Tajima S, Seyama Y (2006) Clin Biochem 39 746-753... 

Kieffer TL, Finucane MM, Nettles RE, Quinn TC, Broman KW, Ray SC, Persaud D, SUiciano RF (2004) Genotypic analysis of HIV-1 drug resistance at the limit of detection virus production without evolution in treated adults with undetectable HIV loads. J Infect Dis 189(8) 1452-1465 Kinoshita S, Su L, Amano M, Timmerman LA, Kaneshima H, Nolan GP (1997) The T cell activation factor NF-ATc positively regulates HIV-1 replication and gene expression in T cells. Immunity 6(3) 235-244... 

YOSHINO G, KAZUMI T, AMANO M, TATEIWA M, YAMASAKI T, TAKASHIMA S, IWAI M, HATANAKA H,... 

The low-temperature method was then applied to the resolution of ( )-2-hydroxy-2-(pentafluorophenyl)acetonitrile (7) (Fig. which is usahle for the syntheses of a variety of ethane diols, amino alcohols containing CgFj groups as novel chiral ligands. After screening lipases such as Amano PS and AK, lipase LIP Pseudomonas aeruginosa lipase immobilized on Hyflo Super-Cel, Toyobo,... 

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