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

• Published in: Carbohydrate research 1983-04, Vol.115, p.59-73
• Main Authors: Cupps, Thomas L., Wise, Dean S., Townsend, Leroy B.
• Format: Article
• Language: English
• ISSN: 0008-6215; 1873-426X
• 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 ( 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 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.