ITERATIVE METHODOLOGY FOR THE STEREOCONTROLLED SYNTHESIS OF POLYOL CHAINS EMPLOYING 2-ACETYLTHIAZOLE AS LACTALDEHYDE EQUIVALENT

The anti-diastereoselective addition (ds 90-92%) of the lithium enolat e of 2-acetylthiazole to chiral (poly)alkoxy aldehydes and the stereoc ontrolled ketone reduction of the resultant aldols using diisobutylalu minum hydride/tetramethylammonium triacetoxyborohydride followed by th e aldehyde unmasking from the thiazole ring, afford three-carbon highe r homologue aldehydes bearing a syn- or anti-1,3-diol unit. The iterat ive repetition of the sequence provides a route to polyhydroxylated ch ains having 1,3- and 1,2-diol units. In this methodology 2-acetylthiaz ole serves as the surrogate of lactaldehyde and its lithium enolate as the equivalent of the alpha-hydroxypropanal beta-anion synthon.