Chiral templates carbohydrates

Kunz H., Mueller B., Pfrengle, W., Rueck K., Staehle W. Carbohydrates As Chiral Templates in Stereoselective [4 + 2 Cycloaddition Reactions ACS Symp. Ser. 1992 494 131-146... 

In some sugar-based lactones, the carbohydrate moiety can serve as a chiral template. For example, the synthesis and characterisation of a novel chiral bicyclic caprolactone 1 was reported in 2003 in six steps from 1,2,5,6-di-O-isopropylidene-a-D-glucofuranose.10 The introduction of... 

The regio- and stereo-selective functionalization of aldonolactones yields optically active lactones, which are important precursors in natural product synthesis. Concepts such as chiral templates and chirons, derived from carbohydrates, have been ingeniously and widely applied in synthesis (233). Among the commercially available aldonolactones, D-ribono-1,4-lactone is... 

Use of Carbohydrates as Chiral Templates for the Synthesis of the Lipid Portion... 

Since the synthesis of glycolipids involves the synthesis of both the lipid and the oligosaccharide portions, we shall also discuss that part of the recorded lipid synthetic work which has involved the use of carbohydrates. In fact, some of the first-recorded applications of carbohydrate molecules as chiral templates are to be found in the lipid field particularly with the use of 1,2 5,6-di-O-isopropylidene-D-mannitol [33] as a precursor of chiral glycerol derivatives for the synthesis of phospholipids and glycolipids based on glycerol and with the use of glucosamine derivatives for the synthesis of phytosphingosines [34] and since this area has not previously been reviewed, it will be treated with a more historical perspective. 

The sequence of Ugi-4CR + hydrolysis of the amino substituent has been employed in the stereoselective synthesis of chiral a-amino acid derivatives, by using a chiral amine component. Then the chiral template was covalently bound in close proximity to the newly synthesized chiral center. The amine residue of the product must be removable under mild conditions to avoid decomposition of the desired product. Chiral a-ferrocenylamines have been employed with some success [34], but the most useful auxiliaries were carbohydrate amines [35]. 

Kunz. H. and 5ichanzenbach, D., Carbohydrates as chiral templates stereoselective synthesis of (i-aminoacids,Angew. Chem. [nl. Ed. Engl.. 28, 1068, 1989. 

Kunz, H. and Pficngle, W., Carbohydrates as chiral templates stereoselective tandem Man-nich-Michael reanions for tithesis of piperidine alkaloids Angew. Chem. Ini. Ed. EngL. 28, 1067, 1989. 

Staehle, W, Kunz, H, Carbohydrates as chiral templates stereoselective Diels-Alder synthesis with dienes of differing reactivity, Synlett, 260-262, 1991. 

Kunz, H, Sager, W, Schanzenbach, D, Decker, M, Carbohydrates as chiral templates stereoselective Strecker synthesis of D-a-amino nitriles and acids using 0-pivaloylated D-galactosylamine as the auxiliary, Liebigs Ann. Chem., 649-654, 1991. 

Kunz, H, Pfrengle, W, Carbohydrates as chiral templates asymmetric Ugi-synthesis of a-amino acids using galactosylamines as the chiral matrices. Tetrahedron, 44, 5487-5494, 1988. 

Kunz, H, Mohr, J, Carbohydrates as chiral templates reactivity and stereoselectivity of carboxylic ester enolates, 7. Chem. Soc. Chem. Commun., 1315-1317, 1988. 

Hanessian, S, Approaches to the total synthesis of natural products using chiral templates derived from carbohydrates, Acc. Chem. Res., 159-165, 1979. 

A stereochemical control of the Ugi reaction can be effected with carbohydrates as chiral templates (e.g. tetrakis(O-pivaloyl)galactosylamine), which gives rise to easily separable amides. From these a variety of non-natural amino acids can be derived after acidic hydrolysis. The Passerini reaction, related to the Ugi rearrangement, gives a-hydroxyamides. A modification of this reaction using titanium tetrachloride gives a-branched amides in high yields via C-metalated imidoyl chlorides (equation 38). 

The high selectivity of M IPs is demonstrated when an optically active compound is imprinted the resulting MIP will normally resolve the racemate. Numerous reports on MIP chiral stationary phases have appeared [184—188]. Chiral templates studied include amino acids [26, 29, 120, 139, 189-192], peptides [139, 192, 193], carbohydrates [58, 194, 195] and dmgs [127, 196]. 

In this article we provide a broad overview of the application of radical methods in carbohydrate chemistry, including typical examples classified by the type of bond formed. The factors controlling the stereoselectivity of inter- and intramolecular C-C bond formation are now well understood and have been exploited in the synthesis of C-glycosides [2]. Intramolecular C C bond formation using carbohydrate-based chiral templates also provides a powerful route to branched-chain sugars [3] and carbocycles [4]. Finally, we include synthetically useful processes involving key carbon-heteroatom and C-H bond formation. 

In order to examine the stereochemical implications in the synthesis of (largely) phosphinic acids (but also tertiary phosphine oxides), Inch and coworkers " employed carbohydrate frameworks as chiral templates. As primary substrates, the cyclic phospho-rochloridate 161 and the corresponding phosphorofluoridate 162 were prepared from methyl 1,2,3-di-O-methyl-a-D-glucopyranoside, each phosphoryl halide being obtained as a mixture of diastereoisomers, anomeric at phosphorus, and from which, in each case, the major component (thought to have an equatorial P=0 bond) was isolated. Configurations in both substrates and reaction products were assigned with the aid of proton and NMR... 

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