A stereocontrolled synthesis of (R)- and (S)-azatyrosine

摘要

An asymmetric synthesis of (R)- or (S)-azatyrosine,starting from (2S)- or (2R)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine (5) (Schollkopf reagent) and 5-benzenesulfonyloxy-2-hydroxymethylpyridine (3),is reported.The diastereocontrolled addition gives mainly one of two possible adducts with the (2S,5R) or (2R,5S) configuration respectively.After the removal of the chiral auxiliary and benzenesulfonyloxy group,azatyrosine is obtained in good yields and high ee.