Differential behavior of (25R)-5,6-epoxyspirostan-22 alpha-O-3 beta-ol and (25R)-5,6-epoxyspirostan-22 alpha-O-3 beta, 4 beta-diol toward Dowex.
The acid-catalyzed hydrolytic cleavage of the 5,6-epoxyspirostane derivatives by the cation exchange resin Dowex 50W X8 has been exploited with the goal of developing synthetic protocols toward 3,4,5,6-polyhydroxyspirostane analogs that can serve as intermediates to potential biologically active compounds. Whereas the diastereomers (25R)-5 alpha, 6 alpha-epoxyspirostan-22 alpha-O-3 beta-ol and (25R)-5 beta, 6 beta-epoxyspirostan-22 alpha-O-3 beta-ol yield two products, (25R)-6 beta-methoxyspirostan-22 alpha-O-3 beta, 5 alpha-diol and (25R)-spirostan-22 alpha-O-3 beta, 5 alpha, 6 beta-triol on Dowex treatment in water-methanol, the alpha- and beta-diastereomers of the 5,6-epoxy derivative of 3 beta, 4 beta-diol provide a single product, (25R)-3 beta, 6 beta-dihydroxy-5 alpha-spirostan-4-one, in good yields. The structures of these products have been confirmed using 1H NMR, 13C NMR, and 1H-1H J-correlated spectroscopies. Multifunctional product formation suggests tremendous utility of Dowex in steroid synthesis. The product formation has been rationalized on the basis of differential conformational constraints of the A/B rings of the different epoxides in directing the reaction course. The reaction shows an interesting example of stereoelectronic effect of a single hydroxy group in discriminating solvent participation.
Korde
S S
SS
Department of Chemistry, Indian Institute of Technology, Powai, Bombay, India.
Baig
M H
MH
Desai
U R
UR
Trivedi
G K
GK
D000837:Anion Exchange Resins / Q000737:chemistry*; D006868:Hydrolysis; D008968:Molecular Conformation; D015394:Molecular Structure; D012117:Resins, Synthetic; D013150:Spirostans / Q000737:chemistry*; D013237:Stereoisomerism
C102560:5,6-epoxyspirostan-22-O-3,4-diol; C102559:5,6-epoxyspirostan-22-O-3-ol; D000837:Anion Exchange Resins; D012117:Resins, Synthetic; D013150:Spirostans; C077982:Dowex 50