21072-68-4

Upstream product

• 108-24-7 acetic anhydride 
• 750-59-4 3β-acetoxycholest-5-en-19-ol 
• 1258-07-7 (3S,5R,6R,8S,9S,10R,13R,14S,17R)-5-bromo-13-methyl-17-((R)-6-methylheptan-2-yl)hexadecahydro-6,10-(epoxymethano)cyclopenta[a]phenanthren-3-yl acetate 
• 1258-35-1 (3S,5R,6R,8S,9S,10R,13R,14S,17R)-5-bromo-6-hydroxy-10,13-dimethyl-17-((R)-6-methylheptan-2-yl)hexadecahydro-1H-cyclopenta[a]phenanthren-3-yl acetate 
• 604-35-3 Cholesteryl acetate 

Downstream Products

• 76010-30-5 19-norcholesta-5(10),6-dien-3β-ol p-toluenesulfonate 

Relevant academic research and scientific papers

Synthesis of the 8,19-Epoxysteroid Eurysterol A

We report the first chemical synthesis of eurysterol A, a cytotoxic and antifungal marine steroidal sulfate with a unique C8?C19 oxy-bridged cholestane skeleton. After C19 hydroxylation of cholesteryl acetate, used as an inexpensive commercial starting material, the challenging oxidative functionalization of ring B was achieved by two different routes to set up a 5α-hydroxy-7-en-6-one moiety. As a key step, an intramolecular oxa-Michael addition was exploited to close the oxy-bridge (8β,19-epoxy unit). DFT calculations show this reversible transformation being exergonic by about ?30 kJ mol?1. Along the optimized (scalable) synthetic sequence, the target natural product was obtained in only 11 steps in 5 % overall yield. In addition, an access to (isomeric) 7β,19-epoxy steroids with a previously unknown pentacyclic ring system was discovered.