Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 4/28/2000
Publication Date: N/A
Technical Abstract: Highly selective asymmetric alpha-hydroxylation of fatty acids has been achieved through chiral imide enolates. Four chiral imides of oleic acid were prepared by reaction of the oleic acid with pivaloyl chloride followed by reaction with four different lithiated oxazolidones including (R)-(+)-4- benzyl-2-oxazolidinone, (S)-(-)-4-benzyl-2-oxazolidinone, (4R,5S)-(+)-4-methyl-5-phenyl-2-oxazolidinone, and (4S,5R)- (-)-4-methyl-5-phenyl-2-oxazolidinones in 88-92% yields. The chiral imides were reacted with NaN(TMS)2 at -78C to give enolates, which subsequently reacted with 2- (phenylsulfonyl)-3-phenyloxaziridine to give alpha- hydroxylated products in 78-83% yields. Diastereomeric excess (de) of the products was determined to be very high (98-99% de) by 1HNMR study after methanolysis of the chiral imide with magnesium methoxide and esterification of the hydroxy group with (S)-(+)-O-acetylmandelic acid. Enantioselective alpha-hydroxylation of other fatty acids including elaidic acid, petroselinic acid, vaccenic acid, and linoleic acid were evaluated under the same condition with (4R,5S)-(+)-4-methyl-5-phenyl-2-oxazolidinone as a chiral auxiliary to give 98% de.