Synthesis of N-trifluoroacetyl-L-acosamine, N-trifluoroacetyl-L-daunosamine, and their 1-thio analogs.
A simple and efficient route to N-trifluoroacetyl-L-acosamine (13), N-trifluoroacetyl-L-daunosamine (12), and their 1-thio analogues (18 and 20) is described. Stereoselective reduction of oxime 5 with borane, followed by trifluoroacetylation resulted in the arabino methyl glycoside (8), which, on mild acid hydrolysis gave N-trifluoroacetyl-L-acosamine (13) in an overall yield of 33%, based on L-rhamnal (1). Upon oxidation of the C-4 hydroxyl group and stereoselective reduction of the resulting ketone 11, compound 8 of L-arabino configuration was converted into N-trifluoroacetyl-L-daunosamine (12) in a one-flask sequence with an overall yield of 28% calculated for 1. Benzyl 1-thio-N-trifluoroacetyl-alpha-L-acosaminide (18) was synthesized from enone 2 on Michael-type addition of phenylmethanethiol, followed by oximation, stereoselective reduction with borane and subsequent trifluoroacetylation. 4-O-Acetyl-1-S-acetyl-N-trifluoroacetyl-1-thio-beta-L-daunosamine 20 was prepared from 12 via the corresponding glycosyl chloride derivative.
D002236:Carbohydrate Conformation; D055598:Chemical Phenomena; D002621:Chemistry; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D006595:Hexosamines / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D013329:Structure-Activity Relationship
D006595:Hexosamines; D007202:Indicators and Reagents; C007217:daunosamine