1-phenylethyl octanoate

The one-pot dynamic kinetic resolution (DKR) of ( )-l-phenylethanol lipase esterification in the presence of zeolite beta followed by saponification leads to (R)-l phenylethanol in 70 % isolated yield at a multi-gram scale. The DKR consists of two parallel reactions kinetic resolution by transesterification with an immobilized biocatalyst (lipase B from Candida antarctica) and in situ racemization over a zeolite beta (Si/Al = 150). With vinyl octanoate as the acyl donor, the desired ester of (R)-l-phenylethanol was obtained with a yield of 80 % and an ee of 98 %. The chiral secondary alcohol can be regenerated from the ester without loss of optical purity. The advantages of this method are that it uses a single liquid phase and both catalysts are solids which can be easily removed by filtration. This makes the method suitable for scale-up. The examples given here describe the multi-gram synthesis of (R)-l-phenylethyl octanoate and the hydrolysis of the ester to obtain pure (R)-l-phenylethanol. 

R)-l-Phenylethyl octanoate ( 2 g) was heated at reflux with IM NaOH (30 mL) overnight. 

Synonyms Phenethyl octanoate 2-Phenethyl octanoate Phenylethyl caprylate Phenylethyl octanoate 2-Phenylethyl octanoate... 

Phenylethyl octanoate 2-Phenylethyl octanoate. See Phenethyl caprylate Phenylethyl phenylacetate 2-Phenylethyl phenylacetate p-Phenylethyl phenylacetate. See Phenethyl phenylacetate Phenylethyl propanoate. See Phenethyl propionate... 

Esters constituted the largest family and included acetates (ethyl, propyl, isobutyl, butyl, isoamyl, and phenethyl), ethyl esters of fatty acids (propanoate, isobutanoate, butanoate, hexanoate, octanoate, 3-hydroxybutanoate, 3-hydroxyhexanoate and furcate), ethyl esters of organic acids (pyruvate, lactate, ethyl myristate, diethyl malate and, mono- and diethyl succinate) and various other esters, such as methyl butanoate, isobutyl lactate and phenylethyl octanoate. The acids quantified included isobutanoic, butanoic, hexanoic, octanoic, decanoic, lauiic and 3-methylbutanoic. The lactones included y-butyrolactone, pantolactone, y-decalactone and E- and Z-oak lactone and the terpenes included neral d-terpineol, P-dtronellol and Z-nerolidol. The aldehyde family comprised acetaldehyde, benzaldehyde, furfural, 5-methylfurfural and octanal, and the phenol family included eugenol, 4-ethylphenol and 4-ethylguaiacol. Finally, 1,1-diethoxyethane, acetoin, sotolon, 2, 3-butanedione, p-cymene and methionol were also determined. 

Acid zeolites have also been tested for the racemisation of alcohols under biphasic conditions. Their scope was found, however, to be limited to benzylic alcohols, since electron-rich benzylic alcohols were not suitable substrates because of the formation of dimers. Under optimised conditions, based on the use of H-Beta zeolite, CAL-B lipase and an excess of vinyl octanoate at 60°C, enantiopure (i )-l-phenylethyl octanoate (>99% ee) was obtained in... 

Acid zeolites have also been tested for the racemisation of alcohols under biphasic conditions.Their scope was found, however, to be limited to benzylic alcohols, since electron-rich benzylic alcohols were not suitable substrates because of the formation of dimers. Under optimised conditions, based on the use of H-Beta zeolite, CALB lipase, and an excess of vinyl octanoate at 60 °C, enantiopure (R)-l-phenylethyl octanoate (>99% ee) was obtained in 90% yield from 1-phenylethanol. In addition, Lozano et al. have recently performed the DKR of this alcohol in the presence of acidic zeolite catalysts (CBV400) in an ionic liquid-supercritical carbon dioxide system with a continuous reaction system. Therefore, when Novozym 435 was employed at 50 °C and 100 bars in the presence of vinylpropanoate as the acyl donor, the expected (R)-phenylethylpropionate was produced in excellent yield of 98% with enantioselectivity of 97% ee and without any activity loss during 14 days of operation. 

Among esters, compounds relevant in the characterization of the fruity aroma of wine are isoamyl acetate, hexyl acetate, 2-phenylethyl acetate and the ethyl esters of the hexanoic, octanoic and decanoic acids. Diethyl succinate is considered as an index of wine ageing and bacterial activity. For all these compounds and the corresponding fatty acids, there is a good linear correlation between XAD-2 enrichment and Kaltron liquid-liquid extraction. A little higher extraction, related to the internal standard, of Kaltron with respect to XAD-2 resin is obtained for most esters and acids, but not for the diethyl succinate and the... 

Figure 5.1. HS (headspace)-SPME-GC/MS chromatogram recorded in the analysis of a Gewiirztraminer wine volatiles performed using a CAR-PDMS-DVB fiber and the experimental conditions reported in Table 5.1. (1) ethyl hexanoate (2) 2- and 3-methyl-1-butanol (isoamyl alcohols) (3) ethyl lactate (4) 1-hexanol (5) ethyl octanoate (6) 1-heptanol (internal standard) (7) benzaldehyde (8) linalool (9) ethyl decanoate (10) diethyl succinate (11) a-terpineol (12) 2-phenylethyl acetate (13) 2-phenylethanol (14) octanoic acid.

As part of their metabolism, all yeasts are known to produce a wide range of esters such as ethyl acetate, isoamyl acetate, isobutyl acetate, ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and 2-phenylethyl acetate (Nykanen and Nykanen, 1977 Soles et al., 1982 Edwards et al., 1990 Webster et al., 1993 Rojas et al., 2001 2003 Plata et al., 2003 Lee et al., 2004). Esters are synthesized through reaction of alcohols (commonly, ethanol) and carboxylic acids by different acyltransferases or ester synthases (Mason and Dufour, 2000). Factors that affect ester synthesis include grape maturity, sugar content, fermentation temperature, and juice clarity (Houtman et al., 1980a 1980b Edwards etal., 1990). 

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