Synthesis of Heterocyclic Compounds by Ring Transformations of 2-Formyl Pentose Glycals

ABSTRACT 2-Formyl-D-xylal 2A and 2-formyl-L-arabinal 2B were reacted with hydrazines to furnish the 4-[1,2-bis(benzyloxy)-3-hydroxypropyl]-1H-pyrazoles 3A-F. Treatment of 2B with 5(3)-aminopyrazole-4-carboxylates 5A-D in the presence of NaH afforded the ethyl 6-[1,2-bis(benzyloxy)-3-hydroxypropyl]pyrazolo[1,5-A]pyrimidine-3-carboxylates 6A-D. Ring transformation of 2A,B with 2-aminobenzimidazole yielded the 3-[1,2-bis(benzyloxy)-3-hydroxypropyl]benzo[4,5]imidazo[1,2-A]pyrimidines 7A,B.