| Abstract
| - The intramolecular reductive coupling of a series of simple orpolyoxygenated oxime ethers δ- orε-functionalized with bromide, α,β-unsaturated ester, aldehyde,or ketone groups is reported. Thecyclization of a nitrile-tethered aldehyde is also studied. Thesereductive couplings are promotedby tributyltin hydride or samarium diiodide. The reactions proceedunder mild conditions, in goodchemical yield, and with high stereoselectivity. When applied tohighly functionalized substratesderived from carbohydrates, this approach provides a selective entry toenantiomerically pureaminocyclitols of varying regio- and stereochemistry. Inparticular, the reductive coupling reactionof carbonyl-tethered oxime ethers promoted by samarium diiodide can beperformed in a one-potsequence, following a Swern oxidation step, allowing the directtransformation of hydroxyl-tetheredoxime ethers into the corresponding aminocyclitols. Moreover, theresultant O-benzylhydroxylamineproducts of these cyclizations can be further reduced insitu with excess samarium diiodide, in thepresence of water, to the corresponding amino alcohols in excellentyields. Some transformationsof these compounds are discussed.
|
