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Stereospecific synthesis of hydroxylated steroid side chains. Synthesis of 25,28-dihydroxy-7,8-dihydroergosterol and its c-24 epimer via [2,3] sigmatropic rearrangement.

✍ Scribed by M.Mark Midland; Young C. Kwon

Book ID: 104233283
Publisher: Elsevier Science
Year: 1985
Tongue: French
Weight: 205 KB
Volume: 26
Category: Article
ISSN: 0040-4039
DOI: 10.1016/s0040-4039(01)80841-8

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✦ Synopsis

LiCzCC(CH3)20TBDMS (t-butyldimethylsilyl) to the aldehyde gave two isomers (4 and 5) in a 1:l ratio. At this point the two C-22 epimers were separated by chromatography in order to achieve the stereospecifit synthesis of the two C-24 epimers. The less polar isomer was assigned as the (22R)-steroid 4.2ctd Compound 4 could be prepared more efficiently by asymmetric reduction of ketone 6 with Alpine-borane4 ((+)-a-pinene, 92% e.e.). Compound 4 is obtained in a greater than 125:l ratio by this process. The asymmetric reduction of 6 is reinforced by the neighboring chiral center.5

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✍ F.J. Sardina; A. Mouriño; L. Castedo 📂 Article 📅 1983 🏛 Elsevier Science 🌐 French ⚖ 214 KB

An efficient, stereospecific synthesis of 25-hydroxy-7,8-dihydroerqosterol, starting from the aldehyde 3 (7 steps, 30,: overally was developed. Key steps are the stereospecific displacement of an allylic carbamate by