Furfuryl alcohols, asymmetric synthesis

Sharpless catalytic asymmetric dihydroxylation of 2-vinylfuran followed by treatment of the diol product with NBS, and subsequent Jones oxidation and Luche reduction provided a highly functionalized a,(1-unsaturated y-lactone in 70% yield overall giving a key intermediate in the synthesis of phomopsolide C <02TL8195>. Similar procedures were adopted by the same authors to synthesize 2-deoxy and 2,3-dideoxyhexoses <02OL1771>. As depicted below, Sharpless kinetic resolution was also used to prepare a pyranone from a furfuryl alcohol in 38% yield, which served as the intermediate in the synthesis of (+)-isoaltholactone <02T6799>. 

Scheme 4. Asymmetric synthesis of chiral furfuryl alcohols...

Kinetic resolution of secondary allylic alcohols by Sharpless asymmetric epoxidation using fert-butylhydroperoxide in the presence of a chiral titanium-tartrate catalyst has been widely used in the synthesis of chiral natural products. As an extension of this synthetic procedure, the kinetic resolution of a-(2-furfuryl)alkylamides with a modified Sharpless reagent has been used . Thus treatment of racemic A-p-toluenesulphonyl-a-(2-furfuryl)ethylamine [( )-74] with fert-butylhydroperoxide, titanium isopropoxide [Ti(OPr-/)4], calcium hydride (CaHa), silica gel and L-(+)-diisopropyl tartrate [l-(+)-DIPT] gave (S)-Al-p-toluenesulphonyl-a-(2-furfuryl)ethylamine [(S)-74] in high chemical yield and enantiomeric excess . Similarly prepared were the (S)-Al-p-toluenesulphonyl-a-(2-furfuryl)-n-propylamine and other homologues of (S)-74 using l-(+)-D1PT. When D-(—)-DIPT was used, the enantiomers were formed . ... 

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