Carbohydrate, chains structural reporter groups

In Sections II, 1 and 2, have been described the 1H-n.m.r.-speUiaI parameters, namely, the chemical shifts, coupling constants, and line widths of the structural-reporter groups of the monosaccharide constituents, of a wide diversity of N-glycosylic carbohydrate chains of glycoproteins. 

Hi) The n.m.r.-spectral parameters of the structural-reporter groups bear the essential information necessary for the elucidation of the primary structure of the carbohydrate chain. If consistent series of structurally related compounds are available for both types of N-glycosylic, carbohydrate structure, a number of empirical, additivity rules for the chemical shifts of the structural-reporter groups can be deduced, as outlined in Section 11,3. 

Typically a hept-6-enyI radical will cyclize much slower than the corresponding hex-5-enyl radical, and often significant proportion of the primary radical is trapped before cyclization, and the olefinic product results. However, with the appropriate substituents or an activated acceptor, hepenyl radical cyclization can be used to prepare 6-membered carbocycles from carbohydrate precursors. For example, Redlich et al. [35] reported that 1,2-dideoxyhept-l-enitol derivatives can be cyclized to carbahexose derivatives [Eq. (II)]. Even though structural requirements (protecting groups, configuration of atoms in the carbon chain, and... 

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