Preparation of Novel 2,3,8-Trisubstituted Pyrido[3,4-b]pyrazines and Pyrido[2,3-b]pyrazines.

A four-step synthesis of 8-bromo-2,3-disubstituted pyrido[ 3,4-b]pyrazines and a six-step synthesis of 8-amino-2,3-disubstituted pyrido[3,4-b]pyrazines have been developed. A particularly valuable feature of this synthetic route is the possibility to build 2,3- disubstituted pyrido[3,4-b]pyrazines with a large variety of substituents in position 8 (aniline, amide, urea, thiourea). Our protocol was extended to the synthesis of 2,3,8-trisubstituted pyrido[2,3-b]pyrazines. [ABSTRACT FROM AUTHOR]