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Various pyrazino[ 1,2-~:4,5'-a']diindoles have been synthesized corresponding in structure t o the diketopiperazine type dimers o f indole-and indoline-2-carboxylic acids. 7,14-Dihydroxy-6H,13H-pyrazino[l,2-a:4,5-~']diindole-6,13-dione reacted w i t h sulfur monochloride and pyridine t o give epidithio and epitrithio derivatives. These are aromatic analogues o f the aranotins. T h e structure o f the epitrithio derivative was verified by single-crystal x-ray crystallography. T h e space group is P?,P21Pz, w i t h pertinent cell data as follows: a = 9.199 (4), b = 13.846 (4), c = 13.248 (3) A, and 2 = 4.

Under Mannich reaction conditions (diethylamine and formaldehyde in toluene under reflux) lasalocid (1) undergoes a unique transformation in which the carboxyl group is replaced by a diethylaminomethyl group. The resulting Mannich base 2 was converted back to lasalocid, proving that none of the other chemical and stereochemical features of the molecule were disturbed. Like other phenolic Mannich bases, the one derived from lasalocid readily alkylated mercaptans. The known thermal and base‐induced retro‐aldol degradations of lasalocid both produce a ketone fragment 9 containing the cyclic ether units. Baeyer‐Villiger oxidation of this ketone afforded a carboxylic acid fragment which still contained these ether units. The normal regiochemistry involved in oxidizing this ketone (RCH2COCHR′R″ type) was cleanly reversed by first converting it into the hydroxymethylidene derivative 10.

A rearrangement reaction has been developed in which o-halobenzylidene derivatives of 3-quinuclidinone are converted to tetrahydropyrido[l,2-a]indoles. These products possess three of the rings, the two-carbon side chain, and a strategically located ketone function which make them readily amenable to elaboration into the Scheme I