Pyridoxal phosphate and an enzyme, tryptophan synthetase, catalyze the last step in the

Chapter 26, Problem 26.46

(choose chapter or problem)

Pyridoxal phosphate and an enzyme, tryptophan synthetase, catalyze the last step in the biosynthesis of the amino acid tryptophan (see Fig. P26.46, p. 1370). (a) The first part of this reaction involves the reaction of pyridoxal phosphate with serine to form species A, an imine of the unstable amino acid dehydroserine. [The red carbon is for part (b).] Assuming that bases (B;) and acids (+BH) are available as needed, give a curved-arrow mechanism for the formation of A. (b) Show with appropriate resonance structures that the carbon shown in red in the structure A has carbocation character. (c) Recognizing that indole derivatives readily undergo electrophilic aromatic substitution at carbon-3,