Methyl 5-hydroxyhexanoate

The enantiomeric excess (ee) of the hydrogenated products was determined either by polarimetry, GLC equipped with a chiral column or H-NMR with a chiral shift reagent. Methyl lactate and methyl 3-hydroxybutanoate, obtained from 1 and 2, respectively, were analized polarimetry using a Perkin-Elmer 243B instrument. The reference values of [a]o(neat) were +8.4° for (R)-methyl pyruvate and -22.95° for methyl 3-hydroxybutcinoate. Before GLC analysis, i-butyl 5-hydroxyhexanoate, methyl 5-hydroxyhexanoate, and n-butyl 5-hydroxyhexanoate, obtained from 1, 5, and 6, respectively, were converted to the pentanoyl esters, methyl 3-hydroxybutanoate was converted to the acetyl ester, and methyl 4-methyl-3-hydroxybutanoate obtained from 2 was converted the ester of (+)-a-methyl-a-(trifluoromethyl)phenyl acetic acid (MTPA). 

Males of the carpenter bee, Xylocopa hirutissima, establish and defend territories that are located proximate to projecting trees on mountain tops (146). These territories are maintained by a mandibular gland secretion that contains, as a major constituent, the cis-lactone of 2-methyl-5-hydroxyhexanoic acid (XXXVIII) (147). 

Suppose a starting material A contains both a ketone and an ester, and it is necessary to selectively reduce the ester to an alcohol (6-hydroxy-2-hexanone), leaving the ketone untouched. Such a selective reduction is not possible in one step. Because ketones are more readily reduced, methyl 5-hydroxyhexanoate is formed instead. 

Wheeler et al. (1976) showed that the secretions of Xylocopa hirsutissima (Xylocopinae) are dominated by c/5-2-methyl-5-hydroxyhexanoic acid lactone. In addition, traces of benzaldehyde, />-cresol, benzoic acid, and vanillin were detected. 

All four possible diastereomers of 2-methyl-5-hydroxyhexanoic acid lactone (628) have been synthesized by Pirkle and Adams (641) and await comparison with natural material to determine which is the pheromone of the carpenter bee. 

Lipase-catalyzed polymerizahon of oxyacid esters was reported. PPL catalyzed the polymerizahon of methyl 6-hydroxyhexanoate. ° The polymer with DP up to 100 was synthesized by polymerization in hexane at 69°C for more than 50 days. The PPL-catalyzed polymerization of methyl 5-hydroxypentanoate for 60 days produced the polymer with DP of 29. Solvent effects were... 

Enzymatic enantioselective oligomerization of a symmetrical hydroxy diester, dimethyl /Lhydroxyglutarate, produced a chiral oligomer (dimer or trimer) with 30-37% ee [24]. PPL catalyzed the enantioselective polymerization of e-substituted-e-hydroxy esters to produce optically active oligomers (DP < 6) [25]. The enantioselectivity increased with increasing bulkiness of the monomer substituent. Optically active polyesters with molecular weight of more than 1000 were obtained by the copolymerization of the racemic oxyacid esters with methyl 6-hydroxyhexanoate. 

Reduction of methyl 4 5-epoxy-2-hexenoate over platinum has been reported to give methyl 4-hydroxyhexanoate and methyl ]m- uiu> ate itself,1776 Incomplete reduction likewise yields these products, hnr in addition also methyl 2-hexenoate. It was concluded that two paralU-l processes are operative (Eq- 346). The first involves reduction nf the double bond, followed by opening of the epoxide ring the second, direct... 

Tertiary alcohols are oxidized in water-dioxane-NaOH to alkoxy radicals, wliich fragmentate to ketone and alkyl radicals R- (Eq. (216) ). The relative rate of cleavage decreases with R in the order sec -butyl > isopropyl > ethyl > propyl > pentyl > isobutyl > methyl 46 8). Likewise, the bisulfite adduct of cyclohexanone is converted in 20% yield to 4-hydroxyhexanoic acid lactone (160) and 3-hydroxycyclohexanoic acid lactone (161) by anodic fragmentation (Eq. (222) ) 469 ... 

In addition, n-hexanoic acid, methyl (X)-7-hexadecenoate and 4-hydroxyhexanoic acid lactone (T-caprolactone) (XV) have been identified as part of the sex attractant blend. All of these compounds are individually active. 

Ethyl butanoate, 2-methyl-3-buten-2-ol (111), ethyl acetate, ethyl 3-hydroxyhexanoate (112),... 

As shown in Figure 7 ethyl 3-hydroxyhexanoate, isolated from purple passion fruit possessed the (R)-configuration, comparable to the hydroxyacid ester obtained by the reduction with baker s yeast. In contrary to that methyl 3-hydroxyhexanoate, which was isolated from aroma extracts of pineapple, consisted of the (S)-enantiomer (91 %). ... 

Propa, Propanoic acid Buta, butanoic acid Penta, pentanoic acid Hexa, hexanoic acid Hepta, heptanoic acid Octa, octanoic acid Nona, nonanoic acid Deca, decanoic acid Pal, palmitic acid St, stearic acid Piva, trimethylacetic acid Vers, Versatic acid a-BrHexa, a-bromohexanoic acid x-BrSt, a-bromostearic acid Me2(OH)Hexa, 2,5-dimethyl-2-hydroxyhexanoic acid a,a -DAC, a,a -dialkylcarboxylic acid Naph, naphthenic acid cy-PA, cyclopentylacetic acid cy-Hexa, cyclohexanecarhoxylic acid C7-C mix, C7-C9 mixture CB, chlorobenzene cy-Hexn, cyclohexane 1,2-DCE, 1,2-dichloro-ethane (i-Pr)2CO, diisopropyl ketone i-amOAc, isoamyl acetate i-amOH, isoamyl alcohol MIBK, 4-methyl-2-pentanone NB, nitrobenzene n-Hexn, n-hexane PE, petroleum ether TCB, 1,2,4-trichlorobenzene. 

Capillary gas chromatographic investigation of diastereoisomeric derivatives revealed that in analogy to results obtained without precursors the chiral metabolites are present as mixtures of enantiomers. However for only a few of these compounds the ratios of enantiomers are identical with those determined in pineapple without precursors. The enantiomeric compositions of ethyl 3-hydroxyhexanoate and ethyl 3-acetoxyhexanoate are almost opposite to those determined for the naturally occurring methyl esters. 6-Octalactone obtained after addition of 5-oxooctanoic acid to pineapple tissue is almost optically pure (92% S) on the other hand -octalactone is naturally present in pineapple tissue as nearly racemic mixture (Table 1,8). 

Figure 1 shows part of a reconstructed ion chromatogram of a pineapple aroma extract isolated after incubation of pineapple slices with 3-hydroxyhexanoic acid-3-di. GC-MS detection of deuterated compounds showed that the following pathways are active (a) esterification leading to methyl and ethyl esters, (b) dehydration to (E)-2-and (E)-3-hexenoates, and (c) chain elongation to methyl 5-hydroxy octanoate followed by acetylation (methyl 5-acetoxyoctanoate) and cyclization ( 6-octalactone). 

PPL catalyzed the polymerization of methyl esters of 5-hydroxypentanoic and 6-hydroxyhexanoic acids.149 In the polymerization of the latter in hexane at 69 °C for more than 50 days, the polymer with DP up to 100 was formed. Relationships between solvent type and polymerization behaviors were systematically investigated hydrophobic solvents such as hydrocarbons and diisopropyl ether were suitable for the enzymatic production of high molecular weight polymer. Pseudomonas sp. lipase catalyzed the polymerization of ethyl esters of 3- and 4-hydroxybu-tyric acids, 5- and 6-hydroxyhexanoic acids, 5-hy-droxydodecanoic acid, and 15-hydroxypentadecanoic acid.157 Oxyacid vinyl esters were demonstrated as new monomers for polyester production under mild reaction conditions, yielding the corresponding polyesters with A/n of several thousands.276... 

Figure VIII shows the enantiomeric composition of various hydroxy- and acetoxyacid esters and of if -hexa-and -octalactone isolated from pineapple. Methyl 3-hydroxyhexanoate and methyl 3-acetoxyhexanoate are mainly of the (S)-configuration corresponding to intermediates of B-oxidation. The optical purity of the 5-acetoxy esters is lower than of the 3-acetoxy derivatives. The lactones were mainly of the (R)-configuration. Figure IX presents a possible pathway to explain the formation of these compounds. Methyl (S)-(+)-3-hydroxyhexanoate and methyl (S)-3-acetoxyhexanoate may be derived from (S)-3-hydroxyhexanoyl-CoA by transacylation with methanol and acetyl-CoA, respectively. The biosynthesis of 5-hydroxyacids is still unknown, but they may be formed by elongation of 3-hydroxyacids with malonyl-ACP. This hypothesis could explain their varying enantiomeric composition relative to the 3-hydroxyacids. However, hydration of unsaturated acids and/or the reduction of 5-oxoacids may be involved.

Methyl e-hydroxyhexanoate was chosen as a model monomer for the first investigation to determine how important reaction parameters that include enzyme origin, solvent, concentration and reaction time influence its self-condensation polymerization [12]. The degree of polymerization (DP) of the polyester formed followed a S-shaped behavior with solvent log P (—0.5 < log P<5)-with an increase in DP around log P 2.5. Decreasing values of DP in good solvents for polyesters were attributed to the rapid removal of product oligomers from the enzyme surface, resulting in reduced substrate concentration near the enzyme. 

Although alkylation of 3-hydFoxy ester dianions occurs with high diastereofacial selectivity, the aldol reaction of the dianion obtained from methyl 3-hydroxybutanoate with benzaldehyde gives all four dia-stereomeric aldols in a ratio of 43 34 14 9 (equation 117). On the other hand, dianions of 8-hydroxy esters show rather good diastereofacial preferences under the proper conditions. Deprotonation of t-butyl-5-hydroxyhexanoate with lithium diethylamide in the presence of lithium triflate gives an enolate that reacts with benzaldehyde to give aldols (196) and (197) in a ratio of 91 9 (equation 118). Use of the r-butyldimethylsilyl ether instead of the alcohol resulted in no facial preference. 

Methyl-furoic acid Platinum 50 20-60 5-Hydroxyhexanoic acid 5... 

Liu JH, Jen HL, Chung YC (1999) Surface modification of polyethylene membrans using phos-phorylcholine derivatives and their platelet compatibility. J Appl Polym Sci 74 2947-2954 Loh SK, ChooYM, Cheng SF, Ma A (2006) Recovery and conversion of palm olein-derived used frying oil to methyl esters for biodiesel. J Oil Palm Res 18 247-252 Loo C-Y, Lee W-H, Tsuge T, Doi Y, Sudesh K (2005) Biosynthesis and characterization of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from pahn oQ products in a Wautersia eutropha mutant. Biotechnol Lett 27 1405-1410... 

Synonyms 5-Caprolactone 5-Hexanolactone 5-Hexanolide 5-Hydroxyhexanoic acid lactone 5-Methyl-5-valerolactone Tetrahydro-6-methyl-2H-pyran-2-one... 

Ethyl formate Ethyl heptanoate Ethyl trans-3-hexenoate Ethylhexyl isobutyrate Ethyl 3-hydroxybutyrate fragrance, cosmetics Ethyl hydroxyheptyl ketone Ethyl 3-hydroxyhexanoate Ethyl hydroxyoleate Ethyl isobutyrate Ethyl laurate Ethyl levulinate Ethyl 2-methoxybenzyl ether Ethyl 2-methyl butyrate Ethyl methylphenylglycldate Ethyl 2-methylvalerate Ethyl myristate Ethyl neryl ether Ethyl nicotinate Ethyl octanoate 4-Ethyloctanolc acid... 

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