Thomas L. Cupps

A further investigation of the stannic chloride-catalyzed condensation reaction of 1-hexene and 1,2,3,5-tetra-O-acyl-β-d-ribofuranoses

Abstract The reaction of 1-hexene with either 1- O -acetyl-2,3,5-tri- O -benzoyl-β- d -ribofuranose ( 5b ) or 1,2,3,5-tetra- O -acetyl-β- d -ribofuranose ( 5a ) in the presence of stannic chloride leads to the formation of a complex mixture of products. By a combination of 1 H-n.m.r. and mass spectroscopy, the products were shown to be anomeric and diastereomeric mixtures of the 8,9,11-tri- O -acyl-protected derivatives of 7,10-anhydro-1,2,3,4,5,6-hexadeoxy- d - allo ( altro )-undec-4-enitol ( 1 ) and 7,10-anhydro-5-chloro-1,2,3,4,5,6-hexadeoxy- d - allo ( altro )-undecitol ( 2 ). The α anomer of 1 was the predominant anomer, whereas the α and β anomers of 2 were present in approximately equal amounts. It was found that 2 was not formed when trimethylsilyl trifluoromethanesulfonate was used as the catalyst instead of stannic chloride. The acyl-protected sugar 3,6-anhydro-2-deoxy- d - allo ( altro )-heptose ( 3 ), prepared by ozonolysis of 1 , reacted with tert -butoxycarbonylmethyltriphenylphosphorane to give tert -butyl trans -5,8-anhydro-6,7,9-tri- O -acetyl-2,3,4-trideoxy- d - allo ( altro )-non-2-enanate ( 4 ). The basicity of the ylide was sufficient to cause anomerization and resulted in an α,β ratio of 5:1 in the product, 4 .

A novel method for the synthesis of 6,7-unsubstituted pyrrolo[3,2-]pyrimidines

Abstract The synthesis of 2,4-dimethoxypyrrolo[3,2- d ]pyrimidine ( 4 ) is described. This facile, 3-step synthesis involves the bromination of 2,4-dimethoxy-6-methyl-5-nitropyrimidine ( 1 ), and the subsequent conversion of compound 1 into compound 4 .