N-acetylglucosamine derivatives

The Css polyprenol (154) obtained from leaves of Magnolia campbelUi has been shown to be a mixture of cis- and /ran -isomers. The preparation of dolichyl phosphate (155) by a pea cell-free extract has been described. Evidence has been obtained that a lipid, containing 7V-acetylglucosamine, which was obtained from Phaseolus vulgaris hypocotyls, consists of a mixture of the dolichol (156) derivatives dolichyl pyrophosphate N-acetylglucosamine and dolichyl pyrophosphate di-N-acetylchitobiose. ... 

In addition to these BAs, a wide range of minor components has been identified, including Ci, C4 or C6 hydroxylated derivatives as well as their epimers, C27 bile acids, oxo bile acids and conjugates on any of the hydroxyl groups with sulphuric acid, glucuronic acid, glucose or N-acetylglucosamine. 

It is a naturally occurring horny substance which forms the framework of invertibrates(such as crabs, lobsters other mollusca), and is the animal analog of cellulose of plants. Chitin is considered a polymer, constg of more than 100 units of anhydro-N -acetylglucosamine, a deriv of D-glucose. 

Peaks identified penta-O-methyl-mono-O-acetylmyoinositol derived from mono-linked myoinositol, 2,3,6-tri-O-methyl-1,4,5-tri-O-acetylglucitol derived from a 4-linked glucose, and 3,4,6-tri-O-methyI-l, 5,di-0-aeetyl-2-acetamido-2-N-methylglucitol derived from a terminal H-acetylglucosamine. The PMAA sample was chromatographed on a 1.5 m X 2 mm ID column packed with 3% OV-210 in a Finnigan automated GC/MS model 3300/6110. Temperature program 150° to 215°C at 6°C/min. 

Figure 9.9 Structures of some derived sugars. (A) /3-D-Glucuronic acid (B) L-iduronic acid (C) a-D-N-acetylglucosamine (D) a-D-N-acetylneuraminic acid.

Figure 2 Mode of action of the prototypical lantibiotic nisin. (a) The peptidoglycan precursor lipid II is composed of an N-acetylglucosamine-p-1,4-N-acetylmuramic acid disaccharide (GIcNAc-MurNAc) that is attached to a membrane anchor of 11 isoprene units via a pyrophosphate moiety. A pentapeptide is linked to the muramic acid. Transglycosylase and transpeptidase enzymes polymerize multiple lipid II molecules and crosslink their pentapeptide groups, respectively, to generate the peptidoglycan. (b) The NMR solution structure of the 1 1 complex of nisin and a lipid II derivative in DMSO (6). (c) The amino-terminus of nisin binds the pyrophosphate of lipid II, whereas the carboxy-terminus inserts into the bacterial membrane. Four lipid II and eight nisin molecules compose a stable pore, although the arrangement of the molecules within each pore is unknown (5).

The a-C-glycoside derivative 27 was first synthesized in six steps from N-acetylglucosamine as described by Cipolla et al (Scheme 3) (54). The 6-hydroxyl group of compound 27 was then protected as the 6-TBDPS silyl ether followed by 3,4-isopropylidenation to afford compound 28. Based on our previous experience, we decided to double protect the acetamido group at C-2 position in order to avoid cyclic hemiaminal formation later in the scheme when the C-6 position will be oxidized to the corresponding aldehyde. Thus, 28 was treated... 

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