Metalation of diazines

A strategy for the total synthesis of dragmacidin E. Construction of the core ring system

[reaction: see text] The construction of the dragmacidin core ring system by a route that features the application of a new indole annelation reaction sequence is described.

Synthesis of Pyrazine Alcaloids from Botryllus leachi. Diazines 43

[reaction: see text] Regioselective metalation of pyrazines and cross-coupling reactions provides an easy access to botryllazines A and B and to an isomer of botryllazine A with good yields from chloropyrazine.

Dimetalation of pyrazines. a one-pot synthesis of multisubstituted pyrazine C-nucleosides

As a part of our efforts to pursue direct, convergent, and concise methodologies for the synthesis of pyrazine C-nucleosides, we have successfully established a sequential dilithiation-addition method, which allows one to introduce two different functional groups to a pyrazine ring in a one-pot fashion. 2,6-Dichloropyrazine was dilithiated at -100 degrees C and then allowed to react with an electrophile, such as bromine, iodine, or disulfides, followed by a reaction with a protected ribonolactone to afford C-nucleosides. After reduction and deprotection, tetrasubstituted pyrazine C-nucleosides, including 2,6-dichloro-3-iodo-5-(beta-D-ribofuranosyl)pyrazine and 2-bromo-3,5-dichloro-6-(beta-D-ribofuranosyl)pyrazine, were obtained. A tandem reaction sequence occurred when disulfides were used, resulting in the formation of 5,6-bis-methylthio-2-chloro-3-(beta-D-ribofuranosyl)pyrazine and 6-(beta-D-ribofuranosyl)-2,3,5-tris-phenylthiopyrazine.