Stereoselective U-4CRs with 1-amino-5-desoxy-5-thio-2,3,4-O-isobutanoyl-β-d-xylopyranose—an effective and selectively removable chiral auxiliary

The Ugi four component reaction (U-4CR) offers a short and direct route for the synthesis of α-amino acid and peptide derivatives. With 1-amino-5-desoxy-5-thio-2,3,4-O-isobutanoyl-β-d-xylopyranose as a chiral amine component excellent chemical yields and stereoselectivities are obtained. After the U-4CR the chiral auxiliary can be cleaved off selectively under mild conditions. The configuration of one of the products was confirmed by X-ray analysis.