902-16-9Relevant academic research and scientific papers
Modular incorporation of 1-benzyltryptophan into dipeptide hosts that bind acetylcholine in pure water
Beshara, Cory S.,Hof, Fraser
, p. 1009 - 1016 (2011/02/16)
Proteins that recognize and bind quaternary ammonium ions depend on " aromatic-cage " structural motifs that use multiple aromatic residues to engage the side chain's ammonium cation. We introduce herein the use of 1-benzyltryp- tophan (Trp(Bn)) residues as synthetic, unnatural partial analogues of natural aromatic cages. We demonstrate the modular incorporation of these building blocks into simple dipeptide hosts and show that they are capable of binding quaternary ammonium ions in buffered water and in chloroform.
Studies on Gelsemium alkaloids. Total synthesis of (+)-koumine, (+)-taberpsychine, and (+)-koumidine
Magnus, Philip,Mugrage, Benjamin,DeLuca, Mark R.,Cain, Gary A.
, p. 5220 - 5230 (2007/10/02)
The total synthesis of the Gelsemium alkaloids (+)-koumine (2), (+)-taberpsychine (4), and (+)-koumidine (50) has been accomplished starting from (S)-(-)-tryptophan (21), All the synthetic alkaloids are antipodal to the natural compounds. N′ -Benzyltryptophan ((-)-22) was methylated to give 23 which was reductively benzylated to provide (-)-25. Pictet-Spengler condensation of (-)-25 with 2-ketoglutaric acid followed by esterification gave a mixture of diastereomeric methyl esters 27/28. Exposure of (+)-27 and (-)-28 to Dieckmann cyclization conditions provided (+)-29 and (-)-29, respectively. Thus starting from a single enantiomer of tryptophan both antipodes of the tetracyclic β-ketoesters (+)-29/(-)-29 are available. Since (+)-29 was the more readily available antipode, subsequent reactions were conducted with this compound. Conversion of (+)-29 into (+)-31 followed conventional lines. N-Alkylation of (+)-31 with propargyl bromide gave (+)-33 which was converted into (+)-36 by treatment with t-BuMe2SiOTf/Et3N, n-BuLi/CICO2Me, and LiBF4. Exposure of (+)-36 to pyrrolidine/ trifluoroacetic acid gave the (Z)- and (E)-quinuclidines (+)-37 and (+)-38. Methylenation of 38 with Tebbe's reagent gave 39. Both E and Z isomers were taken through the series of transformations to give 43, 45, 47, and 49 and 44, 46, 48, and 50. The structures of (+)-37 and (+)-43 were conclusively established by single-crystal X-ray crystallography. Fragmentation of 49 with methyl chloroformate gave 51 which was reduced with LiAlH4 to give (+)-taberpsychine (4). Treatment of 47 with methyl chloroformate gave the 18-hydroxytaberpsychine derivative 52 which was reduced with LiAlH4 to give 53. Similarly 48 gave 55. When the Z isomer 55 was exposed to the Mitsunubo conditions, (+)-koumine (2) was formed (40%, 72% based upon recovered 55). The E isomer 53 gave (+)-koumine (2) in lower yields at a much reduced rate.
