Various approaches to the construction of aliphatic side chains of steroids and related compounds

An improved synthesis of [26‐2H3]castasterone

“…Stereochemical assignments of the side‐chain fragment in compounds 3 – 11 were made based on literature precedents and extensive NMR studies. The reaction of lithium acetylides with steroidal 22‐aldehydes typically affords a mixture (2:1 − 1.5:1) of (22 R )‐propargyl and (22 S )‐propargyl alcohols . To proceed further with the construction of the side chain, we had to deal with an individual isomer having in mind that the required stereochemistry at C‐24 was to be achieved through 1,3‐chirality transfer from a stereogenic centre at C‐22 .…”

Synthesis of a Highly Potent Antitumor Saponin OSW-1 and its Analogues

“…The resulting unsaturated ester was methylated with MeI (LDA, )78°C). The reaction proceeded with a double bond shift to the ring D to afford the desired (20S)-product 30 (Piatak and Wicha, 1978;Wicha and Bal, 1978;Ibuka et al, 1988a, b). The D-ring double bond was subjected to epoxidation with MCPBA.…”

22,23-Epoxides of Sitosterol and Related 7-Oxygenated Δ5-Sterols

“…In literature, there are communications on the obtaining of 22,23-epoxy derivatives of some phytosterols and their surfactant properties [24,25]; however, no data on the stereochemistry of the isomers obtained and their biological activity have yet been published.…”