Studies on steroidal plant-growth regulators. Part 29. Osmium tetroxide-catalysed asymmetric dihydroxylation of the (22E,24R)- and the (22E,24S)-24-alkyl steroidal unsaturated side chain

Abstract

The osmium tetroxide-catalysed asymmetry dihydroxylation of the (22E,24R)-and (22E,24S)-24-methyl steroidal unsaturated side chain with dihydroquinidine p-chlorobenzoate (DHQD) as chiral ligand gave an 8 : 1 ratio of (22R,23R)- and (22S,23S)-22,23-dihydroxylated products; with a 24-ethyl substituent only a 1.5 : 1 ratio of (22R,23R)- and (22S, 23S)-products was obtained. With the chiral ligand 9-O-(9′-phenanthryl) dihydroquinidine (DHQD-PHN), a 8:1 ratio of (22R,23R)- and (22S,23S)-products was obtained from the (22E,24S)-24-ethyl substituted side chain.