Carbasugar, Amino

The 2-oxygenated lactone 67 was reduced by means of sodium borohydride to give the protected carbasugar 72, which by hydrolysis yielded carba- -D-manno-furanose (73). Similarly, the 2-amino substituted lactone 70b was reduced to carba-5-amino-5-deoxy-a-L-glucofuranose (74) [98a] (Scheme 15). 

The intramolecular nitrone cycloaddition (INC) has been used particularly for the synthesis of amino carbasugars [60, 61]. The following scheme illustrates this strategy (Scheme 16) [60], The cycloaddition of nitrone derived from lactol 49 and an excess of N-methylhydroxylamine occurs from the least hindered face affording the isoxazolidine 51 (85% yield). The amino carbasugar 52 was obtained after the cleavage of the N-0 bond. 

Synthesis of amino/hydroxy substituted cyclopentanes carbasugars... 

Scheme 6.4.4. 2,3-trans-CHD 2 as a precursor of cyclohexane epoxides and (amino-) carbasugars. 

Because the carboxyl group of 2,3-trans-CHD 2 is ideally suited to covalent bonding to a polymeric matrix and, moreover, the transformations are performed under very mild conditions, a diversity-oriented approach to regio- and stereo-isomeric (amino)carbasugars, on a solid surface, is applicable in principle. 

The majority of naturally occurring aminocarbasugars bears the amino functionality located at the pseudoanomeric position however, replacement of one or more hydroxyl groups by amino functions on the carbasugar backbone may offer great opportunities for structural and stereochemical variation. This section is subdivided into three subsections, dealing with the synthesis of validamine, valiolamine, and valienamine-type carbaglycosyl amine structures. 

As part of a wide investigation directed towards the preparation of a small repertoire of aminated carbasugars and amino acids thereof, Rassu and co-workers used dienoxy silane 76 as a homologative nitrogen-containing synthon [7a,b,e]. 

By adding flexibility to the project, carbasugar 245 also acted as the scaffold with which p-D-manno-, and p-D-glucovalienamine, as well as 2-amino-2-deoxy-p-D-glucovalienamine were constructed. 

G. Rassu,L. Auzzas, L. Pinna, F.Zanardi,L. Battistini,andG. Casiraghi, Variable strategy towards carbasugars and relatives as illustrated by diastereoselective synthesis of 1 -deoxy-1 -amino pseudo-(S-D-glucopyranose, Org. Lett., 1 (1999) 1213-1215. 

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