beta-Fragmentation of primary alkoxyl radicals versus hydrogen abstraction: synthesis of polyols and alpha,omega-differently substituted cyclic ethers from carbohydrates.
The beta-fragmentation of primary alkoxyl radicals, described in many cases as low-yielding and plagued by side reactions, can proceed in satisfactory yields using carbohydrate substrates. The only reaction that can compete significantly with the beta-scission is the intramolecular hydrogen abstraction. The ratio of beta-fragmentation to hydrogen abstraction can be varied according to the reaction conditions, the stereochemistry of the substituents (e.g., alpha- or beta-anomeric substituents), and the protecting groups chosen. The carbohydrate substrates are easily prepared, and the mild reaction conditions are compatible with most functional groups. The beta-scission reaction provides an expedient way toward shorter and less common sugar series and also toward alpha,omega-differently substituted cyclic ethers. These units are useful building blocks and are present in many natural products with interesting biological activity.
Boto
Alicia
A
Instituto de Productos Naturales y Agrobiología del C.S.I.C., Carretera de La Esperanza 3, 38206 La Laguna, Tenerife, Spain.
Hernández
Dácil
D
Hernández
Rosendo
R
Suárez
Ernesto
E
D000438:Alcohols / Q000138:chemical synthesis* / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D020650:Combinatorial Chemistry Techniques; D004988:Ethers, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
D000438:Alcohols; D002241:Carbohydrates; D004988:Ethers, Cyclic; C059688:alkoxyl radical