Synthesis of alkylated sugar amino acids: conformationally restricted L-Xaa-L-Ser/Thr mimics

Two synthetic strategies for the generation of delta-substituted pyranoid sugar amino acids (SAAs) are evaluated. The first employs chiral nonracemic tert-butane sulfinamides as key reagents. Regardless of the stereochemistry of the applied sulfinamide, the product formed has a stereochemistry resembling that of a D amino acid at C7. Direct Grignard reaction on formyl-tetra-O-benzyl-beta-D-C-glucopyranoside in the second strategy and subsequent Mitsunobu inversion, yields the L, L-dipeptide isosters.