Journal of Lipid Research, Vol 28, 464-469, Copyright © 1987 by Lipid Research, Inc.
Improved method for the synthesis of 1- or 3-acyl-sn-glycerols
DR Kodali
Optically active 1- or 3-acyl-sn-glycerols were synthesized from 2,3- or
1,2-isopropylidene-sn-glycerols, respectively. The 2,3- or 1,2-
isopropylidene-sn-glycerols were condensed with appropriate long saturated
or unsaturated fatty acids and the resulting acyl isopropylidene compounds
were treated with dimethylboronbromide at - 50 degrees C to give the title
compounds. The ketal cleavage of acyl isopropylidene-sn-glycerols by
dimethylboronbromide to produce the long 1- or 3-acyl-sn-glycerols was
effective and gave good yields (70-90%). The reaction conditions were mild
and there was no acyl migration, as shown by optical rotation of the
monoacyl-sn-glycerols. The synthesis of 2,3-isopropylidene-sn-glycerol was
improved to give an overall yield of 40% from L-arabinose. L-Arabinose was
first converted to its 1,1'- diethylmercapto derivative and then condensed
with 2-methoxypropene to yield
1,1'-diethyl-mercapto-4,5-isopropylidene-L-arabinose. Oxidation of this
compound with sodium periodate followed by reduction with sodium
borohydride under alkaline conditions yielded 2,3-isopropylidene-
sn-glycerol [alpha]22D = -14.90 degrees, neat (Lit. 8 [alpha]22D = - 14.5
degrees, neat; 14 [alpha]25D = -10.8 degrees; methanol C, 16.9). The
optical purity of isopropylidene-sn-glycerols was determined as benzoyl
derivatives on a high performance liquid chromatographic column packed with
a chiral stationary phase.