Search

A synthesis of vincadifformine was conducted to determine the compatibility of a beta-disubstituted enamine intermediate with the enantioselection induced by the chiral ferrocenylethyl N-substituent. Tetracyclic vinylogous urethanes were produced from condensations of the chiral N-ferrocenylethylindoloazepines with the aldehydes. Enantiomerically pure (-)-psi- and (-)-epi-psi-vincadifformines, (+)-ibophyllidine, (+)- and (-)-vincadifformine, (-)-tabersonine and (-)-mossambine were afforded by intermediates which, in turn, were provided by diastereomeric selections.

A synthetic pathway to the C-14 hydroxylated pentacyclic alkaloid mossambline and its hydroxy epimer from an indoloazapine ester was developed. The procedure involves intramolecular reactions between vinyl halides and ketones in the presence of a nickel reagent. These include the generation of a racemic pentacyclic ketone from a tetracyclic vinyl iodide and its conversion to alcohols via condensation by N,S-dimethyl-S-phenylsulfoximine and pyrolysis.

Free radical cyclizations of tetracyclic intermediates resulted in the formation of the pentacyclic alkaloids psi-vincadifformine, and epi-psi-vincadifformine. Intermolecular radical alkylation of the tetracyclic amines with methyl acrylate produced 3-oxovincadifformine, whereas radical alkylation with (Z)-1,3-diiodopropene and subsequent selenoxide elimination and intramolecular Heck reactions resulted in the formation of tabersonine and delta18-tabersonine.

Research has been conducted on disulfide functionality. Results of chemoselective oxidation without further oxidizing the disulfide moiety are presented.

Reports on the syntheses of strychnos and aspidospermatan-type alkaloids. Alternative formation of the pentacyclic strychnos alkaloid skeleton; Radical cyclizations of the bromo and chloro analogues; Mossambine and its enantiomers.