Synthesis of circumdatin F and sclerotigenin. Use of the 2-nitrobenzyl group for protection of a diketopiperazine amide; synthesis of ent-fumiquinazoline G

The Eguchi aza Wittig protocol has been used for the synthesis of sclerotigenin and circumdatin F by selective acylation of the more acidic anilide nitrogen of a benzodiazepinedione without the need for protecting groups. The use of the 2-nitrobenzyl group as a photochemically labile protecting group for the amide nitrogen of a diketopiperazine permits the use of the aza Wittig procedure for the synthesis of fumiquinazoline G.