Trifluoroethyl butanoate

Other important derivatives for the preparation of (i-aminoacids are the corresponding P-aminonitriles. Lipase-catalyzed N-acylations of racemic cis-2-aminocyclopentane and cyclohexane carbonitriles with 2,2,2-trifluoroethyl butanoate have been successfully carried out in organic solvents and ionic liquids [53], PSL yielding better results than CALB (Scheme 7.29). 

The lipase-catalyzed DKRs provide only (/ )-products to obtain (5 )-products, we needed a complementary (5 )-stereoselective enzyme. A survey of (5 )-selective enzymes compatible to use in DKR at room temperature revealed that subtilisin is a worthy candidate, but its commercial form was not applicable to DKR due to its low enzyme activity and instability. However, we succeeded in enhancing its activity by treating it with a surfactant before use. At room temperature DKR with subtilisin and ruthenium catalyst 5, trifluoroethyl butanoate was employed as an acylating agent and the (5 )-products were obtained in good yields and high optical purities (Table 3)P... 

The rather complex furylvinylcarbinol derivative 76 shown in Scheme 4.28 was required in enantiopure form as a key intermediate in the synthesis of the natural product cneorin. The carbinol moiety is heavily substituted with sterically demanding groups. Therefore attempts to resolve the furylvinylcarbinol with CALB or lipase PS-II led to very slow reactions. However, the rarely used enzyme Candida antarctica lipase A (CALA), which is known to act on sterically hindered substrates offers an alternative. Thus acylation of the furylvinylcarbinol 76 with 2,2,2-trifluoroethyl butanoate catalyzed by CALA (immobilized on celite with sucrose at pH 7.9) furnished the enantiomerically enriched propanoate of S-76 and R-76 (Scheme 4.28) [90]. Small-scale experiments gave E > 300. 

Butyl butanoate E > 100 Butyl butanoate E > 100 Trifluoroethyl butanoate DIPE E = 75 Trifluoroethyl butanoate DIPE E = 380 Butyl butanoate/DIPE 1/1 E >1000 Trifluoroethyl butanoate DIPE E > 200... 

Rarely is the substituent on nitrogen modified but there are occasional examples. The racemic bicyclic ft-lactams having medium to large rings have been resolved using enzymes. Lipase PS in the presence of vinyl butanoate converted (48%) racemic r-/3-lactams 210 (n = 3) in dry acetone into resolved CM-alcohol 211 (n = 3) and the rfr-ester 212 (n = 3) with ee 97% (Equation 24). A better result was obtained for racemic cis /3-lactam 210 (n = 5 and 8) when vinyl butanoate, was replaced by 2,2,2-trifluoroethyl butanoate, but the ee for 212 ( = 5) was 82% and the ee value for 212 (n = 8) could not be determined. A similar reaction with racemic rra j-/3-lactam ( = 8) required the use of CAL-B (a lipase from C. antarctica) and vinyl butanoate, and the ee value for the tram-alcohol 213 was 85% but the value for the ester 214 could not be determined <2003TA3805>. 

In contrast to castanospermine, 1-deoxynojirimicine 160 contains a primary hydroxy group as well as a much more nucleophilic amino function. If a small excess of trifluoroethyl butanoate is employed, subtilisin converts this alkaloid preferably into the 6-monoester 161 (Fig. 18-22)1266). However, with 6 equiv. of the acylating agent, the 2,6-diester 162 is formed in 77% yield. This diester 162 may be subsequently deacylated regioselectively at the 6-position by means of several different enzymes. 

The application of lipases in the resolution of racemic p-amino acids and their derivatives has been comprehensively reviewed by Liljeblad and Kanerva [27]. The N-acylation method has been commonly employed in the resolution of p as well as P -amino esters [28-34] (Scheme 14.2). Suitable organic solvents for this reaction have proven to be, among others, diisopropylether, tert-butyl methyl ether, and diethyl ether, whereas the commonly employed acyl donors are butyl butanoate and 2,2,2-trifluoroethyl butanoate. 

Monoacylation by use of lipase/trifluoroethyl butanoate systems occurred predominantly at the 2-position of methyl 6-O-butanoyl-a-D-glucopyranoside and at the 4-posidon of methyl 6-deoxy-a-L-glucopyranoside. Methyl 4,6-O-benzylidene-a- and - D-glucopyranoside were preferentially acetylated at 0-2 and 0-3, respectively, by lipase/vinyl acetate Exposure of the galacturono-6,1-lactone triacetate 32 (see Chapter 16 for its synthesis) to wheat germ lipase gave the diacetate 33 in modest yield. ... 

The regioselectivity of the butanoylation of methyl a-L- and a-D-rhamnoside and fucoside has been examined. Lipase catalysed transesterification from 2,2,2-trifluoroethyl butanoate in THF gave the 4-monoesters in >70% yield from the L-glycosides, while the D-... 

In order to obtain (5 )-selective DKR of secondary alcohols, an enzyme with a complementary (5 )-stereoselectivity was needed, since the lipase-catalysed DKR provides only (R)-products. In this context, Park et al. reported, in 2003, the use of subtilisin instead of lipase, but the commercial form of subtilisin was not applicable to DKR, due to its low enzymatic activity and instability in non-aqueous medium. However, these authors succeeded in enhancing its activity and stability by treating it with a surfactant before use. In these conditions, the combination of subtilisin with an analogue of Backvall s catalyst and trifluoroethyl butanoate as the acylating agent... 

Acylsucioses (19) have become available for the first time by the chemoenzymatic procedure shown in Scheme 3. The I -butanoate and the 6,r-dibutanoate of sucrose were prepared by enzyme-mediated ester transfer from 2,2,2-trifluoroethyl butanoate in anhydrous pyridine, but the analogous reaction with 2,2,2-trifluoroethyl adipate showed little regioselectivity. Exposure of peracetylated sucrose to lipase OF, alcalase, Candida lipase, or chymotripsin caused preferential hydrolysis at 0-6, 0-1, 0-4, and 0-6, respectively, giving the various heptaacetates as the main products, whereas hydrolysis by a Pseudomonas lipase afforded a mixture containing the 2,3,4,6,l, 3, 6 -heptaacetate and the 23>4,6,3, 6 -hexaacetate in 20 and 41% peld, respectively. ... 

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