No abstract

A short new route to the pyrido[2,3,4-kl]acridine ring system has been developed from readily available quinoline precursors involving two key steps: ( i ) a palladium(0)-catalysed Suzuki cross-coupling reaction of 4-chloroquinolines with arylboronic acids, and ( i i ) an intramolecular nitrene insertion reaction of the nitrenes derived from 4-phenyl-5azidoquinolines.

Two unusual homoisoflavanone compounds named lesjunceol (1) and lesjuncerol (2) were isolated from the aerial parts of the methanolic extract of Lespedeza juncea apart from the other known constituents myrcetin and β-sitosterol. All the compounds were characterized on the basis of chemical derivatization and spectroscopic methods.

Palladium-Catalyzed Cross-Coupling Reactions of Arylboronic Acids with π-Deficient Heteroaryl Chlorides.-PdCl2(dppb) is an efficient catalyst for the coupling of monocyclic heteroaryl chlorides, e.g. (I), (IV) and (VI), with arylboronic acids such as (II), while Pd (PPh3)4 is a suitable catalyst for the coupling of chloroquinolines of type (VIII) and (X). -(ALI, N. M.; MCKILLOP, A.; MITCHELL, M. B.; REBELO, R. A.; WALLBANK, P. J.; Tetrahedron 48 (1992) 37, 8117-8126; Sch. Chem. Sci., Univ. East Anglia, Norwich NR4 7TJ, UK; EN)

A Short New Route to the Pyrido(2,3,4-kl)acridine Subunit Common to Pyridoacridine Alkaloids of Marine Origin.-Heating of the azidoquinolines (I) results in cyclization to produce the title compounds (II). Further examples are given in the original paper. The synthesis of (Ia) and (Ib) from 4-chloro-8-methoxyquinoline by nitration, reaction with boronic acid, reduction with iron/acetic acid, diazotization, and substitution reaction with sodium azide is also reported. -(ALI, N. M.; CHATTOPADHYAY, S. K.; MCKILLOP, A.; PERRET-GENTIL, R. M.; OZTURK, T.; REBELO, R. A.; J.