| 摘要 |
<p>Multi-stage preparation of 4,4-dimethyl-5 alpha -cholesta-8,14,24-trien-3 beta -ol (I) is carried out starting with a 3-oxopregn-4-en-21-acid ester derivative. Preparation of 4,4-dimethyl-5 alpha -cholesta-8,14,24-trien-3 beta -ol of formula (I) comprises: (i) reaction of a 3-oxopregn-4-en-21-acid ester of formula (II) with a methylation agent in the presence of a base to give a compound of formula (III); (ii) reduction of (III) to give a compound of formula (IV); (iii) protection of (IV) to give a compound of formula (V); (iv) dehydrogenation of (V) to give a compound of formula (VI); (v) isomerization to give a compound of formula (VII); (vi) alkylation of (VII) to give a compound of formula (VIII); (vii) reduction of the ester group of (VIII) to give a compound of formula (IX); (viii) conversion of the primary OH group of (IX) to a leaving group to give a compound of formula (X); and, (ix) when R<2> = H, directly converting (X) to (I). Alternatively, (X) may be converted to (XI) by reductive removal of the OR<3> group, followed by cleavage of the protecting group. R<1> = H, 1-6C alkyl, phenyl, benzyl or 2-, 3- or 4-methylphenyl; R<2> = H, an aliphatic or aromatic carboxylic acid group, an acetal protecting group or silyl ether; R<3> = SO2R<4>; R<4> = 1-6C alkyl, phenyl, benzyl, 2-, 3- or 4-methylphenyl or 2,4,6-trimethylphenyl. Independent claims are also included for compounds of formula (III)-(XI).</p> |
