Synthesis of an Enantiomerically Pure Serine-Derived Thiazole.
Previously reported methods for preparing enantiomerically pure thiazoles are inadequate for the synthesis of inherently labile O-alkyl serine-derived thiazoles. The intermediateN-Boc-(O-methylseryl) thiazolines are very susceptible to tautomerization, even under neutral conditions (Scheme 5). Herein, it is demonstrated that the choice of N-protecting group is critical to the preservation of enantiomeric purity. Thus, using an N-trityl protecting group, O-methyl serine was converted to the corresponding N-Boc-(O-methylseryl) thiazole 3 with no appreciable epimerization as indicated by (19)F and (1)H NMR of the corresponding Mosher's amide.
Sowinski
Jennifer A.
JA
Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055.
Toogood
Peter L.
PL