2-hydroxypentanoate

Sitophilate [1-ethylpropyl (2S,3 )-2-methyl-3-hydroxypentanoate, 24] is the male-produced aggregation pheromone of the granary weevil (Sitophilus granarius). Its racemate is also bioactive. Almeida synthesized ( )-24 by diaster eoselective hydrogenation of the Baylis-Hillman adduct A to B as shown in Scheme 37 [60]. This high diastereoselectivity could be observed only with TBS-protected ester A to give pure B. 

Optically active 3-hydroxybutanoic acid and its methyl ester were first prepared by McKenzie, Magnus-Levy, and Emil Fischer.3 The biopolymer PHB and mixed polymers containing (R)-3-hydroxybutanoate and (R)-3-hydroxypentanoate were also discovered long ago,4 5 and are now produced on an industrial scale. .7 As described here, depolymerization by transesterification [H+ or Ti(OR)4 catalysis], or by hydrolysis, produces8-9 the corresponding monomeric (R)-esters and (R)-acids 1. The 3-hydroxybutanoic acid can also be prepared by hydrolysis of the ester.2-10... 

It is obtained by the copolymerisation of 3-hydroxybutanolc acid and 3 - hydroxypentanoic acid. PHBV is used In speclalily packaging, orthopaedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation m the environment. 

The 2,5-dibromo-2,5-dideoxy-D-xylono-1,4-lactone (6) (Scheme 2) can also be selectively reduced to give 5-bromo-2,5-dideoxy-D-fhreo-pentonolactone (7) by reaction with either aqueous hydrazine as mentioned above, or by consumption of 1 mole of hydrogen [ 14]. Further reaction with hydrogen and Pd/C leads to 3-hydroxypentanoic acid by an initial reductive elimination [15]. Reduction of the primary bromine in these cases can be obtained by means of tributyltin hydride [25] to give 8. 

K Mori, H Mori, H. Sugai. Biochemical preparation of both the enantiomers of methyl-3-hydroxypentanoate and their conversion to the enantiomers of4-hexanol-ide, the pheromone of Trogoderma glabrum. Tetrahedron 41 919-925, 1985. 

SR,3RS)-2,4-Dimethyl-3-hydroxypentanoic acid Pentanoic acid, 3-hydroxy-2,4-dimethyl-(R, S )-( )- (9) (64869-26-7)... 

Stephen H, Montgomery, Michael C. Pirrung and Clayton H. Heathcock 99 (2SR,3SR)-2,4-DIMETHYL-3-HYDROXYPENTANOIC ACID... 

Preparation of the Enantiomers of Methyl 3-Hydroxypentanoate. A mutant of Candida rugosa oxidizes pentanoic acid to give (R)-3-hydroxypentanoic acid of 93% e.e. (19). The corresponding methyl ester 18 can be purified via its crystalline 3,5-dinitrobenzoate to give (R)-18 of 100% e.e. as shown in Figure 6 (20). 

Reduction of octyl 3-oxopentanoate with baker s yeast furnishes octyl (S)-3-hydroxypentanoate of 97% e.e. After transesterification to the corresponding methyl ester 18, it can be purified as its 3,5-dinitrobenzoate to give (S)-18 of 100% e.e. (21). 

Figure 6. Preparation of the enantiomers of methyl 3-hydroxypentanoate. Reagents a) Candida rugosa b) MeOH-H2S04 (80%) c) 3,5-(02N) C6H3C02H, DMAP, DCC/CH2C12 recrystallization d) K0H/THF-Me0H-H20 e) Saccharomyces cerevisiae (70%) f) K2C03/Me0H.

Mori started with the early introduction of the chiral centre [298] in using (3-oxidation of pentanoic acid A by the yeast, Candida rugosa, IFO 0750 [299]. The obtained (R)-3-hydroxypentanoic acid B was transformed into C in a few conventional steps. The second building block was prepared from methyl 2-pentynoate D conjugate addition of lithium dimethyl cuprate yielded E, which was further converted into the frans-configured vinyl bromide F. Hydro-boration of C yielded G which upon Suzuki s palladium catalysed cross-coupling with F furnished 157 after treatment of the reaction product with hydrochloric acid followed by chromatographic purification. The synthesis of ent-157 used (S)-3-hydroxypentanoic acid. 

Form Supplied in colorless oil commercially available. Analysis of Reagent Purity optical rotation NMR spectroscopy. Preparative Methods the preparation of (5, 5)-ethyl-DuPHOS is based on (3R,61 )-octane-3,6-diol as an enantiomerically pure starting compound. The latter is synthesized by a three-step procedure starting from methyl 3-oxopentanoate, which is transformed to methyl (l )-3-hydroxypentanoate (99% ee) by enantioselective hydrogenation with a Ru-(R)-BINAP catalyst, followed by hydrolysis to the hydroxy acid. The subsequent electrochemical Kolbe coupling reaction leads to (3R,6R)-octane-3,6-diol in a protocol that can be scaled up to multigram quantities (eq 1). ... 

Other Enantiopure Dioxinones for Self-regeneration of the Stereogenic Center. The principle of preparing dioxinones from enantiopure p-hydroxy acids was also applied to 3-hydroxypentanoic acid, 4,4,4-trifluoro-3-hydroxybutanoic acid, 4,4,4-trichloro-3-hydroxybutanoic acid, and (5)-serine aldehydes other than pivaldehyde and ketones may be used for dioxinone preparation as well. Furthermore, numerous other dioxinones have been prepared from the parent compound (1) (eqs 3, 4, 6 and 7). The dibromide intermediate... 

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