1.Radiosynthesis of 1-[18F]fluoroethyl-L-tryptophan as a novel potential amino acid PET tracer.
Sun T1, Tang G, Tian H, Wang X, Chen X, Chen Z, Wang S. Appl Radiat Isot. 2012 Apr;70(4):676-80. doi: 10.1016/j.apradiso.2011.11.062. Epub 2011 Dec 7.
(18)F labeled natural amino acids have been introduced as promising tumor imaging agents. A novel [(18)F]fluoro amino acid analog 1-[(18)F]fluoroethyl-L-tryptophan (1-[(18)F]FETrp) was designed and synthesized by a two-pot three-step procedure, including the synthesis of 1-[(18)F]fluoro-2- (tosyloxy)ethane, the [(18)F]fluoroethylation of the precursor N-Boc-L-tryptophan ethyl ester and following the deprotection of the tert-butoxycarbonyl and ethyl ester protecting groups. 1-[(18)F]FETrp was resulted in 0.9 ± 0.2% (n=5) radiochemical yields (no decay corrected) by HPLC purification, within a total synthesis time of 65 min. The radiochemical purity of 1-[(18)F]FETrp was 95-97%. The radiosynthetic method needs to be further optimized to get a satisfying radiochemical yield.
2.Expedient synthesis of threo-beta-hydroxy-alpha-amino acid derivatives: phenylalanine, tyrosine, histidine, and tryptophan.
Crich D1, Banerjee A. J Org Chem. 2006 Sep 1;71(18):7106-9.
An expedient synthesis of enantiomerically pure threo-beta-hydroxy-alpha-amino acid derivatives of phenylalanine, tyrosine, histidine, and tryptophan is described. The NBS-mediated radical bromination of the N,N-di-tert-butoxycarbonyl protected alpha-amino acids and subsequent treatment with silver nitrate in acetone provided the trans-oxazolidinones predominantly. Cesium carbonate catalyzed hydrolysis then generated the beta-hydroxy amino acid derivatives in excellent overall yield.
3.Origin of second harmonic generation optical activity of a tryptophan derivative at the air/water interface.
Mitchell SA1. J Chem Phys. 2006 Jul 28;125(4):44716.
Second harmonic generation optical activity (SHG-OA) of chiral monolayers of the tryptophan derivative N(alpha)-(tert-butoxycarbonyl)-tryptophan (BOC-Trp) at an air/water interface has been studied in detail. In combination with previously reported experimental measurements with the fundamental frequency variant Planck's 'h/' omega=2.20 eV (lambda=564 nm), new measurements with lambda=564 and 800 nm fully characterize the nonlinear susceptibility tensors of chiral and achiral (racemic) monolayers under two-photon resonant and nonresonant conditions of the fundamental frequency. A realistic computational approach including semiempirical, intermediate neglect of differential overlap (ZINDO/S) calculations has been used to calculate the nonlinear susceptibilities of model achiral and chiral monolayers composed of indole chromophores. There is satisfactory agreement between calculated and observed nonlinear susceptibilities, which constrains certain structural parameters of the monolayers including the absolute orientation of the long molecular axis of indole at the air/water interface.
4.Oxidative modification of tryptophan residues exposed to peroxynitrite.
Kato Y1, Kawakishi S, Aoki T, Itakura K, Osawa T. Biochem Biophys Res Commun. 1997 May 8;234(1):82-4.
The aim of this study was to clarify the mechanism of loss of Trp residues in proteins exposed to peroxynitrite. The Trp residues in bovine serum albumin and collagen IV were decreased by peroxynitrite treatment. To identify the degradation products of the Trp residue by peroxynitrite, tert-butoxycarbonyl-L-tryptophan (Boc-Trp) was used as a model of the Trp residue in proteins, and the products formed from peroxynitrite-treated Boc-Trp were then isolated. Boc-Trp decreased with an increase in peroxynitrite concentration. N-Formylkynurenine, oxindole, and hydropyrroloindole were identified as major products. The formation of these products may account for the losses of Trp residues in proteins by peroxynitrite.
