Add time:07/20/2019         Source:sciencedirect.com

Enantioselective synthesis of C23–C28 subunit of campestane steroids based on catalytic methods is reported. The synthesis was started from (S)-2-isopropyl-4-nitrobutan-1-ol, which is easily accessible by the reaction between isovaleraldehyde and nitroethylene catalyzed by only 2% of (S)-trimethylsilyldiphenylprolinol. Removal of one “extra” carbon from the nitroalcohol was achieved by Ni-catalyzed hydrodecarboxylation of the redox-active ester intermediate. The synthesized C23–C28 fragment was attached to a steroidal core by Julia-Kocienski reaction of a steroidal aldehyde with metallated C23–C28 sulfone. The obtained product of olefination was easily transformed to a precursor of campesterol and (Z)-22-dehydrocampesterol.

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