A FURTHER INVESTIGATION OF THE STANNIC CHLORIDE-CATALYZED CONDENSATION REACTION OF 1-HEXENE AND 1,2,3,5-TETRA-O-ACYL-β-D-RIBOFURANOSES

Article abstract of DOI:10.1016/0008-6215(83)88135-X

The reaction of 1-hexene with either 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (5a) or 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose (5b) in the presence of stannic chloride leads to the formation of a complex mixture of products.By a combination of 1H-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.