The structure of itesmol and its C-24 congenor.
Abstract Structures 1 and 2 respectively have been assigned to itesmol and its minor congener isolated from a cactus indigenous to Mexico.
Stereoselective synthesis of 24-alkyl-22-hydroxysterols based on chelation-controlled radical reactions
We have shown that the diastereoselectivity in the radical-mediated reactions of steroidal 24-methylene-22-oxy-25-oic acid esters 6–11 with alkyl iodides performed in the presence of Lewis acid MgBr2·OEt2 depends on the bulk of the alkyl iodides, the oxy groups at C-22 and the configuration at C-22. The ethylation of 9 afforded the syn-adduct exclusively and the methylation of 6 and 7, ethylation of 10 and isopropylation of 9 gave syn-adducts with high selectivities (syn–anti = 8.8–5.1∶1). Other combinations, except for the tert-butyl radical addition to 6, 7 and 10 predominantly yielding anti-adducts, showed lower syn-selectivities.
Zur Chemie Des Ecdysons
Fur das Ecdyson, das Hautungshormon der Insekten, wurde eine verbesserte Isolierungsmethode ausgearbeitet. Rontgenmessungen an Ecdysonkristallen und massenspektroskopische Untersuchungen fuhren ubereinstimmend zu einem Molekulargewicht von 464 und damit zu der revidierten Summen-formel C27H44O6. Durch Messung der diffusen Rontgenstreuung und durch Dehydrierung zu Cyclopentenophenanthren-Derivaten wird bewiesen, das das Edcyson zu den Steroiden gehort. Die Sauerstoffatome liegen in Form einer Oxogruppe und von fuf Hydroxylgruppen vor. Die Position dieser Gruppen wird diskutiert.