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2005
Steroids
U 0300
11- 192
On Steroids. Part 418. Synthetic Approach to 5α-Pregnanolone 19-[O-(Carboxymethyl)oxime] Derivatives. — Two 5α-pregnanolone derivatives possessing
3α- and 3β-configuration are synthesized from pregnene derivative (I). An initial protection of the 20-oxo function as a cyclic ketal via silyl protection of the 19-hydroxy
group affords the corresponding ketal in 78% overall yield. However, since this sequence is not suitable for a larger scale, the use of silyl protection during acetalization
is bypassed by preparation of diacetate (IV), which is converted into a ketal by the triethyl orthoformate method. The different reactivity of the acetyl groups allows selective deprotection of the 3-acetyl group. In the 3β-series, position 3 in (VI) is protected
followed by liberation of position 19. The synthesis of 3β-epimer (X), suitable as a hapten for isopregnanolone, is accomplished by using standard methods. — (CERNY, I.;
HAVLIKOVA, H.; HILL, M.; HAMPL, R.; POUZAR*, V.; Collect. Czech. Chem.
Commun. 69 (2004) 9, 1805-1817; Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep.,
CZ-166 10 Prague 6, Czech Republic; Eng.) — H. Hoennerscheid
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