Preparation of a furfural-derived enantioenriched vinyloxazoline building block and exploring its reactivity

<i>N-</i>Alloc-protected furfuryl amino alcohols derived from furfural and ʟ- or ᴅ-valinol were subjected to Torii-type ester electrosynthesis to obtain the corresponding unsaturated esters. These served as key intermediates to prepare (<i>S</i>)- and <i>(R)-</i>enantioenriched unsaturated amides by <i>N</i>-Alloc deprotection which induced concomitant methoxymethyl group cleavage, <i>O-</i>to-<i>N</i> rearrangement, and isomerization of the double bond. An oxazoline ring formation in the resulting unsaturated amides provided the corresponding enantioenriched vinyloxazoline. The reactivity of the electron-deficient double bond in the vinyloxazoline was explored in several reactions. Out of these, the aza-Diels-Alder reaction with TsNCO was successful, leading to a highly diastereoselective formation of an oxazolo[3,2-<i>c</i>]pyrimidine derivative.