| |
[摘要]：An easy entry to the 1-oxaspiro[4.4]nonane skeleton has been developed starting from a D-glucose-derived substrate. The key steps involve (a) installation of olefin moieties at the appropriate places through simple transformations and (b) construction of spiro rings by utilizing ring-closing metathesis reactions between these olefin functionalities. Subsequent deprotection of the acetonide functionality, peracetylation, nucleosidaton under Vorbruggen reaction conditions, and final deprotections result in the formation of the spironucleosides. The involvement of an interesting intra/intermolecular acetyl migration has been used to rationalize the product distribution during desilylation. Various 1D and 2D NMR techniques and X-ray analyses of some important intermediates were used for assigning the structures and stereochemistry of the products. |
|
