Increased dipeptoid diversity resulting from post-condensational manipulation of the Ugi reaction products

5,6-Dihydropyrazolo[1,5-a]pyrazines prepared via the Ugi reaction involving pyrazole-3-carboxylic convertible tert-butyl isocyanide and subsequent microwave-promoted cyclization, were found to be prone to opening with primary and secondary amines, thereby providing a facile, three-step access to a greater diversity of Ugi-type dipeptoids, some of which cannot be accessed via the Ugi reaction itself.