Treatment of sodium N-(o-azidobenzoyl)aminoacylglycinates 8 with acetic anhydride afforded 1-acetyl-4-(o-azidobenzoyl)-2,5-piperazinediones 7, with complete retention of the stereochemistry. The intramolecular aza Wittig reactions of compounds 7 in the presence of tributylphosphine followed by deacetylation gave 1,2-unsubstituted pyrazino[2,1-b]quinazoline-3,6-diones 1. This route was adapted to the synthesis of both enantiomers of the alkaloid glyantrypine.

p-Tolyllead triacetate efficiently arylates the nitrogen atom of carboxamide, sulfonamide, imide, and hydantoin anions under mild conditions. This reaction did not interfere with the arylation of amino and β-dicarbonyl groups.