Bicyclic Compounds Derived from Tartaric Acid and α-Amino Acids (BTAas): Synthesis of New Molecular Scaffolds Derived from the Combination of (R,R)-Tartaric Acid andL-Serine

Abstract

The synthesis of the new N-Fmoc-protected dipeptide isoster methyl (1S,2S,5S,6R)-2exo-hydroxymethyl-7,8-dioxa-3-azabicyclo[3.2.1]octane-6exo-carboxylate (BTS) has been achieved, starting from (R,R)-tartaric acid and O-benzyl-L-serine, in 11% overall yield after 9 steps. Interestingly, starting from the same α-amino acid, it was also possible to prepare the 2endo-substituted compound, formally derived from the combination of tartaric acid with D-serine. Each compound has a CH2OH functional group at C-2, which is very useful for greater diversification of the 7,8-dioxa-3-azabicyclo[3.2.1]octane-6-carboxylate (BTAa) dipeptide isosters. The oxidation of the C-2 carbinol group in BTS, moreover, gave rise to a novel, conformationally constrained, α-amino acid that may find application in peptidomimetic synthesis.