Abstract:
:Two variants of the Claisen rearrangement were evaluated for a stereoselective construction of a C-25 stereogenic center in cholestenoic acids based on 1,4-chirality transfer. Johnson orthoester Claisen rearrangement of (22R)- and (22S)-propargyl enol ethers proceeded in a highly stereoselective manner to give (25R)- and (25S)-isomeric allenes. The stereochemical outcome of the Ireland-Claisen rearrangement of 22-allylic alcohols was dependent on the configuration of the C-22 hydroxyl group and the geometry of the enol ether. The latter could be controlled by the solvent (THF or a mixture of THF/HMPA) chosen for the generation of silyl enolate.
journal_name
Steroidsjournal_title
Steroidsauthors
Ermolovich YV,Zhabinskii VN,Khripach VAdoi
10.1016/j.steroids.2013.03.006subject
Has Abstractpub_date
2013-07-01 00:00:00pages
683-92issue
7eissn
0039-128Xissn
1878-5867pii
S0039-128X(13)00064-0journal_volume
78pub_type
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