Fragmentation of Carbohydrates

D. J. Harvey, T. S. Mattu, M. R. Wormald, L. Royle, R. A. Dwek, and P. M. Rudd, Internal residue loss Rearrangements occurring during the fragmentation of carbohydrates derivatized at the reducing terminus, Anal. Chem., 74 (2002) 734-740. 

C. G. Francisco, C. C. Gonzalez, and E. Suarez, Fragmentation of carbohydrate anomeric alkoxy radicals. A new synthesis of alduronic acid lactones, Tetrahedron Lett., 37 (1996) 1687-1690. 

Fig. 4. Nomenclature of fragments of carbohydrates as defined by Domon and Costello.32 This figure is adapted from ref. 31.

Scheme 32 Synthesis of chiral vinyl sulfones via a DlB/l2-promoted oxidative fragmentation of carbohydrates...

As part of a study of the stereochemical dependence of geminal C-H coupling, the sign of in the OCCH fragment of carbohydrates... 

Considering only a fragment of carbohydrate molecule (i.e. dioxycarbohydrates) we can find some analogy with hydrocarbons. It helps the students in learning more about the carbohydrates and their inter-relationship with oxygen compounds. 

Scheme 7. Fragmentation of Carbohydrates under Oxidative Conditions. DIB = (diacetoxyiodo)-benzene.

Scheme 12. Fragmentation of Carbohydrates under Reductive Conditions.

Additional examples of this methodology include the synthesis of 1,1-difluoro-l-iodo alditols 583 [627], 2-azido-l,2-dideoxy-l-iodo-alditols 585 [628,629] and chiral vinyl sulfones 587 [630] by fragmentation of carbohydrate anomeric alkoxy radicals generated from the respective carbohydrates 582, 584 and 586 (Scheme 3.231). 

Figure 6.12 The Domon and Costello nomenclature system for fragmentations of carbohydrate chains. Reprinted from Ref [91] with kind permission from Springer.

The stability of azides in radical reactions is further illustrated by the radical fragmentation of carbohydrate anomeric aUcoxyl radicals bearing an azido substituent at position 3 reported by Suarez (Scheme 8.2). After fragmentation, the 2-azido-substituted radical is iodinated and no jS-fragmentation of the azide is observed. 

Figure 193. Nomenclature introduced by Domon and Costello S for describing the fragmentation of carbohydrates.

Lattova, E. Snovida, S. Perreault, H. Krokmn, O. Influence of the labeling group on ionization and fragmentation of carbohydrates in mass spectrometry. J. Am. Soc. Mass Spectrom. 2005,16, 683-696. 

Suarez et al. have reported a general method for the synthesis of alduronic acid lactones via fragmentation of carbohydrate anomeric alkoxy radicals [124] (Scheme 77). Treatment of hexopyranose derivative of the galacturonic acid, 342, with (diacetoxyiodo)benzene and iodine under mild conditions or with... 

Schemes 51,52, and 53 outline an extension of the method by the tandem P-fragmentation-cyclization sequence to modify the carbohydrates by the iodosylbenzene-iodine reagent instead of DIB-iodine. Thus, the transformations of D-ribofuranose to 3-O-formyl-a-D-erythrofuranose (Scheme 51), furanose to cyclic ketoses, such as alduronic acid lactones (Scheme 52), and carbohydrates to five- and-six-membered azasugars (Scheme 53) can be achieved. P-Fragmentation of carbohydrate suitably substituted by azide group resulted in the formation of chiral nitriles (Scheme 54). ...

Armas, d.R, Francisco, C.G., and Suarez, E, Reagents with hypervalent iodine formation of convenient chiral synthetic intermediates by fragmentation of carbohydrate anomeric alkoxy radicals, Angew. Chem. Int. Ed. Engf., 31, 111, 1992. 

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