Stereospecific 7α-alkylation of 20-hydroxyecdysone in a lithium–ammonia solution

• For the first time stereoselective 7α-alkylation of ecdysteroids was accomplished.
• Efficient syntheses of novel 7α-alkylecdysteroids as potential pharmacologically active compounds.
• The structures of novel compounds were confirmed by NMR (1H, 13C, COSY, NOESY, HSQC and HMBC) and X-ray diffraction analysis.

The reaction of 20-hydroxyecdysone with methyl or ethyl iodide or allyl bromide in a lithium–ammonia solution results in stereospecific 7α-alkylation to give 7α-methyl-, 7α-ethyl-, and 7α-allyl-14-deoxy-Δ8(14)-20-hydroxyecdysones, respectively. By catalytic hydrogenation (Pd-C/MeOH), the 7α-allyl derivative was converted to 7α-n-propyl-14-deoxy-Δ8(14)-20-hydroxyecdysone.

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