A highly efficient total synthesis of dictyodendrins A-E was accomplished. The synthesis features a novel benzyne-mediated one-pot indoline formation/cross-coupling sequence for the construction of a highly substituted key indoline intermediate. Peripheral substituents were introduced onto this intermediate in a modular fashion to complete the total synthesis of dictyodendrins A-E.

The key step in this total synthesis of (-)-acetylaranotin is the efficient formation of the characteristic dihydrooxepine ring from cyclohexenone through an unusual vinylogous Rubottom oxidation and a regioselective Baeyer-Villiger oxidation. (-)-Acetylaranotin is obtained in 22 steps from commercially available L-Cbz-tyrosine (Cbz=benzyloxycarbonyl).

In‐do‐line of fire: A highly efficient total synthesis of the title compounds features a novel benzyne‐mediated one‐pot indoline formation/cross‐coupling sequence for the construction of a highly substituted key indoline intermediate. The peripheral substituents were then introduced onto the intermediate in a modular fashion to complete the total syntheses of dictyodendrin A and B.

The structure of a C-symmetric epidithiodiketopiperazine alkaloid, SCH 64874, was determined by semisynthesis. The relative stereochemistry of the β-hydroxy carboxylic acid chain having three chiral centers was determined by comparison of the NMR data of the four possible diastereomeric β-hydroxy carboxylic acid fragments with those of SCH 64874. Condensation of the (-)-deacetylaranotin core with two enantiomeric β-hydroxy carboxylic acids revealed the relative stereochemistry of SCH 64874. The relative stereochemistry of the β-keto carboxylic acid chain of the analogous alkaloid hirsutellomycin was determined in a stepwise manner. The C4'-C6' syn relationships were predicted by comparing the NMR data of the corresponding ester fragments with that of hirsutellomycin. The relative stereochemistry of the whole molecule, including the epimerizable C2' stereocenter, was determined by introduction of four possible side chains into the bisdethiodi(methylthio)deacetylaranotin core. We found that the stereochemistry of C2' converged with that of the thermodynamically stable form influenced by the core structure.

A benzyne-mediated synthesis of substituted indolines and carbazoles was developed. The reaction includes generation of benzyne using Mg(TMP)2·2LiCl as a base, cyclization, and trapping the resulting organomagnesium intermediate with an electrophile to provide a series of substituted indolines and carbazoles in a regiospecific manner. This was applied to a concise five-pot total synthesis of heptaphylline.