合成路线1

The reaction of vitamin D2 (I) with refluxing liquid SO2 gives a mixture of the 6(R)- and 6(S)-SO2-adducts (II), which by treatment with tert-butyl-dimethylsilyl chloride (TBDMSCI) and imidazole in DMF yields the corresponding mixture of silylated adducts (III). The reaction of the mixture (III) with NaHCO3 in ethanol affords the silylated 5(E)-vitamin D2 (IV), which by oxidation with SeO2 and N-methylmorpholine N-oxide in refluxing methanol-dichloromethane is converted into a mixture of silylated 1(S)- and 1(R)-hydroxy-5(E)-vitamin D2 (V). The silylation of (V) as before, followed by crystallization in ethyl ether-ethanol gives the 1(S)-isomer of the fully silylated compound (VI), which is treated with refluxing SO2 as before to yield the mixture of the 6(R)- and 6(S)-SO2-adducts (VII). The ozonolysis of the mixture (VII) in dichloromethane-methanol at -65 C affords the corresponding mixture of the 6(R)- and 6(S)-SO2-aldehydic adducts (VIII).

合成路线2

The silylation of vitamin D2 (XXIII) with TBDMS-Cl and imidazole in dichloromethane gives the silyl ether (XXIV), which is cyclized with N-sulfinyl-p-toluenesulfonamide yielding the Diels-Alder adduct (XXV). The oxidation of (XXV) with SeO2 and N-methylmorpholine-oxide in ethanol affords the trans-1alpha-hydroxy-3-O-(tert-butyldimethylsilyl)vitamin D2 (XXVI), which is irradiated with UV light in benzene containing anthracene yielding 1alpha-hydroxy-3-O-(tert-butyldimethylsilyl)vitamin D2 (XXVII). Finally, this compound is desilylated with TBAF in THF. The cyclization of the silyl ether (XXIV) can also be performed with Ts-N=Se=N-Ts yielding the corresponding adduct (XXVIII), which is oxidized with SeO2 as before to afford the trans-1alpha-hydroxy-3-O-(tert-butyldimethylsilyl) vitamin D2 (XXVI) already reported.

合成路线3

By allylic oxidation of vitamin D2 (XXIII) with SeO2 and tert-butyl hydroperoxide in pyridine followed by purification by TLC over silicagel. The allylic oxidation of trans-vitamin D2 (XXIX) with SeO2, tert-butyl hydroperoxide and octahydroacridine in dichloromethane gives the trans-1alpha-hydroxyvitamin D2 (XXX), which is isomerized to the target compound by irradiation with UV light with anthracene as photosensitizer.

合成路线4