Synthesis of novel L-phenylalanine derivatives substituted with a keto ylide as stable precursor of a vicinal tricarbonyl moiety

Abstract

Novel L-phenylalanine derivatives 5 containing a vicinal tricarbonyl moiety at the para position of the phenyl ring were prepared in 4 steps starting from N α-Cbz-L-tyrosine benzyl ester. A 7 step reaction sequence lead to N α-Fmoc protected derivatives 9 with the tricarbonyl structure masked as its stable keto ylide precursor, which is suitable for solid phase peptide synthesis. The phosphoranylidene intermediates 8 were transformed to the trioxo compounds 5 with Oxone ® as oxidant