Synthesis and molecular modeling of (4'R)- and (4'S)- 4'-substituted 2'-{[(E)-androst-5-en-17-ylidene]-methyl}oxazolines.

Synthesis of four novel (4'R)- and (4'S)- 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]-methyl} oxazolines, comprising 4'-hydroxymethyl (1 and 2) and 4'-methoxycarbonyl (3 and 4) substituents is presented. Reaction of 17α-bromo-21-iodo-3β-acetoxypregn-5-en-20-one with either (L)-serine methyl ester, or (D)-serine methyl ester resulted in methyl N-[3β-acetoxy-21-oxopregna-5,17(20)-dien-21-yl]-(L)-serinate and methyl N-[3β-acetoxy-21-oxopregna-5,17(20)-dien-21-yl]-(D)-serinate (as mixtures of related [17(20)E]- and [17(20)Z]-isomers). Cyclization of obtained amides led to methyl 2'-{[(E)-3β-acetoxyandrost-5-en-17-ylidene]methyl}-(4'S)-4',5'-dihydro-1',3'-oxazole-4'-carboxylate and methyl 2'-{[(E)-3β-acetoxyandrost-5-en-17-ylidene]methyl}-(4'R)-4',5'-dihydro-1',3'-oxazole-4'-carboxylate which were transformed to titled compounds 1-4. The molecular docking of compounds 1-4 to ligand binding site of nuclear receptor LXRβ revealed significant differences due to stereochemical configuration of 4' atom and structure of 4'-substituent.