The Preparation of Optically Pure 3-Hydroxyalkanoic Acid. The Enantioface-differentiating Hydrogenation of the C=O Double Bond with Modified Raney Nickel. XXXVII.

Abstract

The enantioface-differentiating hydrogenation of methyl 3-oxoalkanoate (CH3(CH2)nCOCH2COOCH3, n=0, 6, 8, 10, 12) over the (R,R)-tartaric acid–NaBr–modified Raney nickel catalyst ((R,R)-TA–NaBr–MRNi) gave methyl (R)-3-hydroxyalkanoate (CH3(CH2)nCH(OH)CH2COOCH3, n=0, 6, 8, 10, 12) in an average optical yield of 85%. After the methyl ester had been converted to dicyclohexylammonium salt of 3-hydroxyalkanoic acid, the salt was recrystallized three times from acetonitrile and then treated with acid to give optically pure (R)-3-hydroxyalkanoic acid (CH3(CH2)nCH(OH)CH2COOH, n=0, 6, 8, 10, 12) in a reasonable yield. From the hydrogenation product with (S,S)-TA–NaBr–MRNi, optically pure (S)-3-hydroxyalkanoic acid was obtained by the same process as above.

Stereoselective Syntheses of Tetrahydroesterastin‐β ‐Lactam Analogues

“…Thus, the known methyl (R)-3-hydroxytetradecanoate (5) [7] was protected as its (tert-butyl)dimethylsilyl ether 6 which was reduced with diisobutylaluminum hydrid (DIBAH) yielding the enantiomerically pure aldehyde 7. The chiral oxa- …”

Pahutoxin: Synthesis and Determination of Its Absolute Configuration

“…3 ) That is, methyl 3-oxohexadecanoate (3) was subjected to enantio-differentiating hydrogenation over (R,R)-tartaric acid-NaBr-modified Raney nickel «R,R)-TA-MRNi) to give (R)-( -)-methyl 3-hydroxyhexadecanoate (87% e.e.). Saponification of the hydrogenated product gave crude 2.…”

Synthesis and purity assessment of tetra- and pentaacyl lipid A of Chlamydia containing (R)-3-hydroxyicosanoic acid

“…To this end, methyl 3-oxoicosanoate 6 was prepared from octadecanoyl chloride 5 via chain lengthening with 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid) and subsequent decarboxylation in 46% yield. 18 Enantioselective Noyori hydrogenation 16,19 of the prochiral 3-oxo-ester 6 in methanol using RuCl 2 [(R)-Binap] at 60 8C and 85 kg cm K2 hydrogen pressure afforded methyl (R)-hydroxyicosanoate 7 in 77% yield with excellent optical purity (eeR99%). Comparison of its specific optical rotation value with those reported for shorter methyl (R)-3-hydroxyalkanoates 14 allowed to assign the absolute configuration of 7 as (R).…”

“…The residue was purified by flash chromatography on silica gel (5:1/4:1 toluene/EtOAc) which afforded 14 as a syrup (1.2 g, 92%). (1,5-dihydro-3-oxo-3l 5 -3H-2,4,3-benzodioxaphosphepin-3-yl)-3-O-tetradecanoyl-2-(2,2,2-trichloroethoxycarbonylamino)-a-D-glucopyranoside (18). A solution of 14 (prepared according to method A) (250 mg, 0.36 mmol), N,N-diethyl-1,5-dihydro-3H-2,4,3-benzodioxaphosphepin-3-amine (260 mg, 1.08 mmol) and 1H-tetrazole (126 mg, 1.8 mmol) in CH 2 Cl 2 (10 mL) was stirred for 20 min under N 2 .…”