Synthesis and chemical reactivity of thiophenoxyphenylalanine bioisosteres, suitable synthons for the design of HIV protease inhibitors

Phenylalanine in which the methylene group is replaced by a sulfur atom cou ld be a useful bioisostere for the design of HIV-protease inhibitors. Due t o the chemical instability of hemiaminal intermediates, these bioisosteres have to be prepared from alpha-hydroxyglycine following specific synthetic routes. In this paper, we report the synthesis of sulfenylated phenylalanin e bioisosteres 2 and 3, which represent two original building-blocks for pe ptide solid phase synthesis.