The synthesis of d-cycloserine has been successfully accomplished from the readily available d-serine through three simple and efficient routes. In each synthetic strategy, cyclization reactions are involved as the key step, and one-pot processes are employed. The simple treatment and mild reaction conditions are attractive features in this methodology.

d-Cycloserine has been successfully synthesized in good yields through three new synthetic routes from a readily available d-serine. In each synthesis, cyclization served as the key step, and two of the routes employed one-pot operations for the preparation of the target product. These methods featured the use of mild reaction conditions and simple treatments.

New synthesis of oseltamivir phosphate was accomplished in 9 steps with a 27% overall yield from a readily available (−)-shikimic acid. Selective ring opening reaction of ketal and azide Mitsunobu reaction for facile replacement of a hydroxyl group by the N3 group at the C-3 position of (3R,4R,5R)-ethyl 4-hydroxy-5-(methoxymethoxy)-3-(pentan-3-yloxy)cyclohex-1-enecarboxylate 4 and at the C-4 position of (3R,4S,5R)-ethyl 4-acetamido-5-hydroxy-3-(pentan-3-yloxy)cyclohex-1-enecarboxylate 7 successfully served as the key steps.