Catalytic asymmetric synthesis of the central tryptophan residue of celogentin C.
[reaction: see text] Chiral phase-transfer catalyst 5 containing an electron-deficient trifluorobenzyl moiety promoted the alkylation of glycine derivative 6 with propargyl bromide 7a in good yield and excellent ee. The resulting propargyl glycine 8 was converted to 14, the central tryptophan residue of Celogentin C, in two steps, with the Pd-catalyzed heteroannulation as the key transformation. This method promises to be an efficient route for the preparation of tryptophan derivatives possessing substitution on the indole ring.
D000478:Alkylation; D002384:Catalysis; D005998:Glycine / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D014364:Tryptophan / Q000138:chemical synthesis*
D010456:Peptides, Cyclic; C445725:celogentin C; D010165:Palladium; D014364:Tryptophan; D005998:Glycine