Pyrimidine‐Annulated Pyrrolobenzodiazepines. A New Ring System Related to Aspergillus Alkaloids

Abstract

Pyrrolo[2,1‐c][1,4]benzodiazepine‐5,11‐dione was converted into the corresponding C‐11‐monothiolactam and subsequently treated with amines to give cyclic amidines, which racemize due to the formation of tautomers (NMR, X‐ray analysis) under basic conditions. We treated these amidines with bis(trichlorophenyl) malonate esters. Formation of neutral tautomers of the 1,3,8‐triones of the new 4,7a,12b‐triaza‐dibenzo[e,g]azulene ring system gave a twisted molecule with both helical and chiral structure elements (NMR, X‐ray analysis), which caused a splitting of the NMR signals into two sets. Results of two X‐ray single crystal analyses are presented, together with an ab initio calculation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

N-Heterocyclic Carbenes of Indazole as Reagents: Indazol-3-ylidene-Mediated Syntheses of Amidines from Thiolactams of Pyrrolobenzodiazepines

“…All pyrrolobenzodiazepines possessing an N10-H group give resonance frequencies of C-9a at approximately d = 133. In contrast to tetracyclic systems which we prepared earlier, 37,38 no C(11)-C(11a) double bonds of tautomer C were detected, although all reactions of aromatic amines lead to almost complete racemization of the pyrrolobenzodiazepines 5gk which can -at least in part -be explained by the intermediary existence of this tautomer. We propose the following mechanism for the indazol-3ylidene-mediated amidination (Scheme 4).…”