A new synthesis of D-galactosamine from D-glucosamine

Carba-Sugar Analogs of Glucosamine-6-Phosphate: New Activators for the glmS Riboswitch

Riboswitches are 5'-untranslated mRNA regions mostly found in bacteria. They are promising drug targets to overcome emerging bacterial resistance against commonly used antibiotics. The glmS riboswitch is unique among the family of riboswitches as it is a ribozyme that undergoes self-cleavage upon binding to glucosamine-6-phosphate (GlcN6P). Previously, we showed that carba glucosamine-6-phosphate (carba-GlcN6P) induces self-cleavage of the riboswitch with a potency similar to that of GlcN6P. Here, we report a synthetic approach to a new class of carba-GlcN6P derivatives with an alkoxy substituent in the carba position. Key features of the synthesis are a ring closing metathesis followed by a hydroboration. The strategy gives access to libraries of carba-GlcN6P derivatives. Ribozyme cleavage assays unraveled new activators for the glmS riboswitch from Listeria monocytogenes and Clostridium difficile.

Oligosaccharides from "standardized intermediates". The 2-amino-2-deoxy-D-galactose analog of the blood-group O(H) determinant, type 2, and its precursors

The selectively benzylated glycoside allyl 2-acetamido-4,6-di-O-benzyl-2-deoxy-beta-D-galactopranoside (4) was prepared from the corresponding derivative of 2-acetamido-2-deoxy-D-glucose via the p-bromobenzenesulfonate and the benzoate. 2-O-Benzoyl-3,4,6-tri-O-benzyl-alpha-D-galactopyranosyl (10) was obtained from allyl 6-O-benzyl-2-O-(2-butenyl)-alpha-D-galactopyranoside via known intermediates. To complete the sequence, the 1-propenyl 3,4,6-tri-O-benzyl galactoside was successively converted into the 2-benzoate, the free sugar, and the chloride 10. A fully protected form (11) of the trisaccharide alpha-L-Fucp-(1 leads to 2)-beta-D-Galp-(1 leads to 4)-D-GalNAc was then synthesized by coupling 10 to 4, partially deblocking the disaccharide product, and L-fucosylating the resulting intermediate. Cleavage of the O-benzyl groups from 11, with concomitant saturation of the allyl group, gave the propyl beta-glycoside of the unsubstituted trisaccharide.