A Straightforward Route to Novel α,α-Disubstituted Tetrahydrofuran β-Amino Acids and Spirodiketopiperazines from Sugar Lactones

Indium-mediated Reformatsky reactions of aldonolactones with ethyl alpha-bromoisobutyrate allowed the synthesis of ulosonic acid esters, which were readily transformed into the corresponding tetrahydrofuran beta-azido esters in a stereoselective fashion. This approach provided monomeric components suitable for oligomerization to the carbopeptoid class of foldamers and prompted the total synthesis of the attractive novel spiro diketopiperazine, which can be regarded as a spironucleoside.