Sugar synthesis furfuryl alcohols

Two approaches, based on furan, have found wide application in carbohydrate synthesis. Cycloaddition reactions of furan with 2-substituted acrylonitrile or acrolein lead to oxabicycloheptanes which, in tnm, can be transformed to monosaccharides. On the other hand, furfuryl alcohols can be converted—either by the Clauson-Kaas reaction or by mild oxidation—into 5,6-dihydro-4-pyrones, suitable for easy functionalization to sugars. 

Dihydro- and 5,6-dihydro-2H-pyrans (266 and 267) continued to be substrates for sugar synthesis. These ring systems are readily available and can be functionalized in a number of ways. In consequence, as in the case of furfuryl alcohols, general methods for carbohydrate synthesis have been developed. 

The Brimble group reported the synthesis of acortatarin A 20 in 2012. As in the first synthesis of acortatarin A 20 by Sudhakar et al. a traditional acid-catalyzed dehydrative spiroketalization was used as one of the final steps. However, instead of performing the previously used disconnection between CIO and N9, as several other groups have reporteda Maillard-type condensation reaction between amino alcohol 50 and the sugar surrogate 51 would be used to give 49. The amine 50 would come from D-mannitol and 51 would be prepared from furfuryl alcohol on a gram scale (Scheme l )" ... 

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