Novel Reactions of Carbohydrates Discovered En Route to Natural Products

✍ Scribed by B. Fraser-Reid; R. A. Alonso; R. E. McDevitt; B. Venkateswara Rao; G. D. Vite; M. A. Zottola

• Publisher: Wiley (John Wiley & Sons)
• Year: 2010
• Weight: 477 KB
• Volume: 101
• Category: Article
• ISSN: 0037-9646
• DOI: 10.1002/bscb.19921010709

✦ Synopsis

An approach t o the synthesis of tetrodotoxin is described in which two key reactions are used to establish the densely functionalized carbocyclic ring. The [3:2:l]-bicyclic framework of 1,6-anhydro mannopyranose serves as the template, and in the first key reaction, oxazolidine ring formation is used to introduce the angular nitrogen and, simultaneously, to preorganize functional groups for the second key reaction. The latter involves formation of the carbocyclic ring uia a radical cyclization process.

The application of free radical procedures in synthetic carbohydrate chemistry has been of long standing interest to our research group, beginning with our report of the conjugate addition of oxycarbinyl radicals to carbohydrate a-enones in 19721 (Scheme 1). This method provided a ready route to branched-chain sugars,2 which has subsequently proved valuable3 Application of this simple reaction t o non-carbohydrate substrates was first demonstrated by Bundy,4 and it still continues to attract interest judging from recent reports.5 Scheme 11