Seven-membered carbohydrate ring

D. Sabatino and M. J. Damha, Oxepane nucleic acids Synthesis, characterization, and properties of oligonucleotides bearing a seven-membered carbohydrate ring, J. Am. Chem. Soc., 129 (2007) 8259-8270. 

J. O. Hoberg, Formation of seven-membered oxacycles through ring expansion of cyclopropanated carbohydrates, J. Org. Chem., 62 (1997) 6615-6618. 

Only short comments will be given for other acetal derivatives that are less popular Chart 1 presents a list of formulae of cyclic acetals, mainly, those with five- and six-membered rings (1,3-dioxolanes and 1,3-dioxanes). Seven-membered ring acetals are omitted because they are scarcely represented in carbohydrate chemistry. The special case of spiroacetah and cydohexane-l,2-diacetal-protecting groups, which have been reported recently, will be presented in Part K. 

W. A. Szarek and J. K. N. Jones, Carbohydrates containing nitrogen in a five-membered ring and an attempted synthesis of a carbohydrate with nitrogen in a seven-membered ring, Can. J. Chem. 43 2345 (1965). 

Currently, there is a lot of interest in nucleoside attached to seven-membered ring carbohydrate derivatives. Conversion of 30 to 31 was discovered serendipitously when wet tin tetrachloride was used instead of an anhydrous sample <1998TL3923>. This led to a useful synthesis of 32 (Scheme 13). 

The Chemistry of D-Apiose. Part II. The Configuration of D-Apiose in Apiin, R. K. Hulyalkar, J. K. N. Jones, and M. B. Perry, Can.]. Chem., 43 (1965) 2085-2091, Carbohydrates Containing Nitrogen in a Five-membered Ring and an Attempted Synthesis of a Carbohydrate with Nitrogen in a Seven-membered Ring, W. A. Szarek and J. K. N. Jones, Can.J. Chem., 43 (1965) 2345-2356. 

Naming of carbohydrate boronates may be based on three principles (a), the central use of the ester heterocyclic rings 1,3,2-dioxaborolane (five-membered), 1,3,2-dioxaborinane (six-membered), and 1,3,5,2,4-trioxadiborepane (seven-membered, for example, 8 and 9) (b), the use of radical prefixes borylene (Chem. Abstr.) or boranediyl (I.U.P.A.C.) for /BH or (c), ester terminology. Thus, for example, according to these respective procedures, the glycerol derivative 10... 

Scheme 4). This cascade RCM applied to diene-ynamides leads to fused az-abicyclic products with good yields [11], and carbohydrates can be used to synthesize polyoxygenated bicyclic systems that contain seven- and eight-membered rings [12]. 

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