Carbamoyl mannose

A superb example of this approach is the total synthesis of bleomycin A2 (252) reported by Hecht. Bleomycin was isolated by Umezawa and co-workers Q nd shown to be a potent anticancer agent.l69 While determining the structure, it was shown that hydrolyses and other chemical manipulations of 252 gave nine identifiable fragments (a) aminopropyldimethyl sulfonium (253) (b) 2-aminoethyl-2, 4-bithiazole-4 -carboxylic acid (254) (c) L-threonine (255) (d) (2f ,3S,4R)-4-amino-3-hydroxy-2-methylpentanoic acid (256) (e) L-eryr/zro-(3-hydroxyhistidine (258) (f) (3-amino-P-(4-amino-6-carboxy-5-methylpyrimidin-2-yl)propionic acid (259) (g) a rearrangement product, L- 3-aminoalanine (257) (h) gulose (260) and, (j) carbamoyl mannose (261). 

This enzyme [EC 3.1.3.9] catalyzes the hydrolysis of o-glucose 6-phosphate to yield o-glucose and orthophosphate. Some glucose phosphatases also catalyze transphosphorylation reactions from carbamoyl phosphate, hexose phosphates, pyrophosphate, phosphoenolpyru-vate and nucleoside di- and triphosphates, using D-glu-cose, D-mannose, 3-methyl-D-glucose, or 2-deoxy-D-glu-cose as phosphoryl acceptors. See Isotope Exchange (Reactions Away from Equilibrium)... 

Treatment of metal-free BLM with triethylamine in aqueous alcohol at room temperature induces migration of the carbamoyl group at 3-0-position of the mannose to 2-0-position to give iso-BLM [32]. Treatment of copper complex of BLM under the same condition causes epimerization at the a-position of the pyrimidine ring to afford pi-BLM (Fig. 6) [33]. /so-BLM and epi-BLM exhibited remarkably lowered antimicrobial activity [32, 33]. 

The introduction of an amino-group into carbohydrates has been achieved by displacement of a tosyloxy or similar leaving group by participation of a neighbouring 0-carbamoyl group (—CONHR). Thus, 2-amino-l,6-anhydro-2-deoxy-j3-D-mannose was prepared from 1,6 3,4-dianhydro-2-0-tosyl- 8-D-glucopyranose as outlined in Scheme 1. A similar reaction has been proposed by Barton and Motherwell/ ... 

Bleomycin A2 (M.W. ca 1400) contains two sugars (1-glucose and 3-0-carbamoyl-p-mannose) and the peptide and amino acids 18-20. -21... 

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