Polyhydroxy-a-amino acids

The synthetic utility of this strategy is demonstrated by the preparation of polyhydroxy-a-amino acid 14 via cyclization of 12 to the corresponding 2-oxazolidinones 13103. 

Casiraghi, G, Rassu, G, Spanu, P, Pinna, L, A-rerr-Butoxycarbonyl-2-(fert-butyldimethyl-silyloxy)pyrrole as a glycine anion equivalent a flexible enantioselective access to polyhydroxy-a-amino acids. Tetrahedron Lett., 35, 2423-2426, 1994. 

Davis, F. A., Prasad, K. R., Carroll, P. J. Asymmetric Synthesis of Polyhydroxy a-Amino Acids with the Sulfinimine-Mediated Asymmetric Strecker Reaction 2-Amino 2-Deoxy L-Xylono-1,5-lactone (Polyoxamic Acid Lactone). J. Org. Chem. 2002, 67, 7802-7806. 

The first attempts to produce a graft copolymer of poly(amino acids) onto the natural polymers, such as cellulose, starch, and their derivatives, were carried out by Zilka and Avny in 1965. Sodium methoxide was known to be an initiator of NCA polymerization. Therefore, they proposed to use alkoxide derivatives of polysaccharides as macroinitiators for the graft copolymerization of NCA s of a-amino acids. All known methods for production of alkoxide derivatives of natural polymers, such as the reaction of polyhydroxy polymers with sodium metal in liquid ammonia, or exchange reactions between lower alkoxides and polyhydroxy polymers, - were unsatisfactory for the subsequent graft copolymerization of NCAs, because any residual base would lead to homopolymerization. In addition, alkoxide derivatives of cellulose acetate and nitrocellulose could not be obtained by these conventional methods due to chemical degradation. Zilka et al., finally found that the reaction of alkali metal naphthalenes [20] with polyhydroxy polymers in either... 

These are the most common class of complex lipid (Figure 12.11) and contain a phosphoric acid residue (phosphate group) and two fatty acids esterified to glycerol. Attached to the phosphate group is an amino alcohol, sometimes referred to as the nitrogenous base, which may be either serine, choline or ethanolamine or sometimes the monomethyl or dimethyl derivatives of ethanolamine (Table 12.4). Alternatively, a polyhydroxy compound which is either glycerol, myo-inositol or one of their derivatives is attached instead... 

Bose, A.K., Banik, B.K., Mathur, C., Wagle, D.R. and Manhas, M.S., Polyhydroxy amino acid derivatives via beta-lactams using enantiospecific approaches and microwave techniques, Tetrahedron, 2000, 56, 5603. 

M. Zajac and A. Jelinska, Effect of amino acids, amines and polyhydroxy compounds on the stability of latamoxef, Pharmazie 46, 115-117 (1991). 

The natural product bengamide A (65) is synthesized via coupling of 3-amino-hexahydro-2-azepinone (64) with optically active polyhydroxy alkanyl carboxylic acid (63). Bengamide A was first isolated from choristid sponge and shows anti-infective activity. 

The retention of sugars, sugar alcohols, amino acids, and hy-droxyacids on polystyrene-based cation-exchange resins has been examined as a function of the counter-ion. Retention of polyhydroxy lie compounds decreased in the order K>Na>Li, due to decreas-... 

Alkylamino-l-deoxy-D-fructoses reacted with potassium isocyanate in the presence of hydrochloric acid to give imidazole derivatives [e.g. (235)], while 1-amino-1-deoxy-D-gi/uco-heptulose gave the 4-[(polyhydroxy)a(kyl]pyrrole (236)... 

A variety of a-amino-polyhydroxy-tetronic and pentonic acids have been synthesized from bromodeoxyaldonolactones. Typically, the 2-broino-2-deoxy-D-xylonolactone (33) gave the epimeric azides (34) as a 1 1 mixture after isolation by chromatography, the D-xylo-azide could be converted to 2-acetamido-2-deoxy-D-xylose (35)... 

A few methods are known for attaching amino acid units to the hydroxyl group of polysaccharides, including the reaction of acid chlorides of amino acids with polyhydroxy polymers in a basic medium,2 or with aminated cellulose derivatives,or amine derivatives, 2 or by simple esterification of the polyhydroxy polymer with N-acetyl amino acids. Single amino acid substituents can not be considered grafts, at best these derivatives could be used as macroinitiators. 

Koskinen, A.M.P. and Chen, J. (1991) Enantiospecific synthesis of polyhydroxy amino acids. Synthesis of the C33-C38 portion of calyculins. Tetrahedron Lett., 32, 6977-6980. 

Figure 12.11 Phosphoglyceride structure. The members of this group are derivatives of the parent compound, l,2-diacyl-src-glycerol-3-phosphate (phosphatidic acid) in which X is a hydrogen atom. This is replaced by either an amino alcohol or a polyhydroxy residue. In phosphoglycerides derived from animal tissues R1 is usually a saturated acyl chain of between 16 and 20 carbon atoms and R2 is usually unsaturated. Polyunsaturated acyl chains containing 16 or 18 carbon atoms predominate in leaf phosphoglycerides and those of bacterial origin are often more complex.

On the other hand, lithium perchlorate catalyzed Diels-Alder reaction between 4-[(ethoxycarbonyloxy)methylene]-2-phenyl-5(47/)-oxazolone 829 and cyclopenta-diene is more efficient and affords a mixture of the corresponding exo-830 and endo-831 cycloadducts. These cycloadducts have been converted to 2-amino-3-hydroxynorbornenecarboxylic acid derivatives 832 and 833 or to 2-amino-3-hydroxynorbornanecarboxylic acids 834 and 835 after a series of careful transformations.In addition, 830 and 831 have been further elaborated to new conformationally constrained serine analogues, the polyhydroxy 2-aminonorbor-nanecarboxylic acids 836-839 as shown in Scheme 7.257. ° ... 

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