Applications of CeCl3 as an Environmental Friendly Promoter in Organic Chemistry

Additional minor ecdysteroid components of Leuzea carthamoides.

Fomentarols A–D, sterols from the polypore macrofungus Fomes fomentarius

Chiral methyl-branched pheromones

Nitrogen-containing ecdysteroid derivatives vs. multi-drug resistance in cancer: Preparation and antitumor activity of oximes, oxime ethers and a lactam.

The 6-oxo group in 2,3:20,22-di-O-isopropylidene derivatives of 20-hydroxyecdysone and its 24,25/25,26-anhydro analog is reduced with NaBH4-CeCl3 in a stereoselective fashion to afford the corresponding 6α-alcohols. In the first case, the reaction is accompanied by dehydration to give Δ14-bond. Reduction of the same substrates with NaBH4 or LiAlH4 in the absence of CeCl3 leads to mixtures of 6α- and 6β-hydroxy derivatives, the latter prevailing. In all cases, epimerization at C5 occurs.

Stereochemistry of Hydride Reduction of 20-Hydroxyecdysone Derivatives

Reactions of 20-hydroxyecdysone, its diacetonide, and 24,25(25,26)-anhydro derivative with lithium tetrahydridoaluminate gave the corresponding 6α- and 6β-epimeric alcohols and 7,8-dihydro analogs.

7,8-dihydro analogs of ecdysteroids

(E)-Oximes derived from 20-hydroxyecdysone diacetonides and 7,8-dihydro analog were converted into the corresponding lactams (6-oxo-5a-aza-5a-homo derivatives) via Beckmann rearrangement. 14,15-Anhydro-20-hydroxyecdysone (Z)-oxime under analogous conditions (reaction with p-toluenesulfonyl chloride in acetone in the presence of Na2CO3) gave rise to 20-hydroxyecdisone 20,22-acetonide (Z)-O-tosyloxime which did not undergo Beckmann rearrangement.

R. V. Shafikov

Papers

Stereochemistry of Hydride Reduction of 20-Hydroxyecdysone Derivatives

7,8-dihydro analogs of ecdysteroids

20-hydroxyecdysone oximes and their rearrangement into lactams

Synthesis of 7,8-dihydro analogs by reaction of 20-hydroxyecdysone derivatives with lithium aluminum hydride

Regio- and stereodirected transformation of 20-hydroxyecdysone to 2-dehydro-3-epi-20-hydroxyecdysone under ozonization in pyridine