Fructose-6-phosphate Aldolase in Organic Synthesis:  Preparation of d-Fagomine, N-Alkylated Derivatives, and Preliminary Biological Assays

d-Fructose-6-phosphate aldolase (FSA) mediates a novel straightforward two-step chemo-enzymatic synthesis of d-fagomine and some of its N-alkylated derivatives in 51% isolated yield and 99% de. The key step is the FSA-catalyzed aldol addition of simple dihydroxyacetone (DHA) to N-Cbz-3-aminopropanal. The use of FSA greatly simplifies the enzymatic procedures that used dihydroxyacetonephosphate or DHA/esters. Some N-alkyl derivatives synthesized elicited antifungal and antibacterial activity as well as enhanced inhibitory activity, and selectivity against β-galactosidase and α-glucosidase.