Saccharide template

R. J. Patch, H. Chen, and C. R. Pandit, Multivalent templated saccharides Convenient syntheses of spacer-linked 1, l -bis -and 1, 1, 1 "-tris-/i-glycosides by the glycal epoxide glycosidation method, /. Org. Chem., 62 (1997) 1543-1546. 

The polymerization of several different protected monomers was executed with the molybdenum initiator. Two types of norbornene templates were generated as mixtures of diastereomers one class possessed a single saccharide substituent attached through either an endo or exo ester group, and the other was equipped with two carbohydrate residues appended to the bicyclic scaffold... 

In carbohydrate chemistry, the most described method for the preparation of saccharidic thionocarbamates involves preliminary introduction of the amine function on a partially or non-protected saccharidic template. The condensation of amino sugars with carbon disulfide or thiophosgene leads to cyclization in 1,3-oxazolidine- or l,3-oxazine-2-thiones. This reaction involves the formation of an intermediate isothiocyanate, which reacts further with a 3- or y-located hydroxyl group. The viability and facility of this process depends on the saccharidic ring size and the inherent strain. Some major rules can be put into light from the cases studied 30... 

This methodology applied to aldohexoses differing in amine position on saccharidic template (anomeric position, C-6, C-2, C-3 or C-5) will be discussed. 

Saccharidic templates bearing an amino group in C-2, C-6, C-3, C-5. Generally, an amine located on non-anomeric position reacts similarly through the condensation reaction with carbon disulfide or thiophosgene, the preliminary formed isothiocyanate leads to spontaneous or base-induced cyclization into 1,3-oxazolidine- or l,3-oxazine-2-thiones, as previously mentioned. Several extensive studies are reported about the selective introduction of thionocarbamate moieties on carbohydrate scaffolds.3 22 23 320 34 38... 

The direct attachment of adequately substituted mexo-arylporphyrin to the saccharide units has been another synthetic strategy. Mexo-tetraaryl-porphyrins were used as templates to append, directly or by a spacer, several sugar units at the ortho, meta or para positions of the phenyl ring (Fig. 1). 

Figure 9 Regioselective bis-functionalization of C60 using a saccharide as an imprinting template.

To perform energy minimization of custom-made saccharides, peptides and other biomolecules (a list of templates is available from http //www.dkfz-heidleberg. 

An interesting templated bis-functionalization was reported by Shinkai and co-workers who introduced two boronic acid groups regio- and diastereo-selectively into C6o by using saccharides or saccharide derivatives as imprinting templates.147-149 Thus, when D-threitol was used as the template, C2-symmetric cis-3 isomers fC-49 and fA-49,150 were obtained in a nearly. 72 28 ratio after removal of the saccharide templates (Scheme 1.6).149 Competitive complexation studies indicated that D-threitol-imprinted boronic acid (fC)-49 and L-threitol-imprinted (A)-49 preferentially rebind their original templates with up to 48% d.e.148 Exploration of other regio- and diastere-oselective double [4 + 2] cycloadditions between C6o and o-quinodimethanes... 

DNA polymerases work by stitching together two nucleotides, one at the 3 end of a DNA chain and the other a deoxynucleic acid triphosphate. The two are held in position near each other by hydrogen bonding to the template DNA chain and are joined by reaction of the first phosphate of the triphosphate with the OH of the saccharide ring of the other base, releasing diphosphate. Mg ions separated by about 390 pm are bound on each side of the phosphorus in the transition state, as in Figure 16-23. 

---