N-Acetyl tryptophan

From the fore gut of Laccophilus minutus, a Bacillus pumilus strain was isolated which produced maculosin, the diketopiperazine formed from proline and tyrosine [103] 24, phenyl malonate 25, N-acetylphenylalanine 26, N-acetyl-tryptophane 27 and 3,4-dihydroxybenzoic acid [ 103]. Maculosin which has also been isolated from several microorganisms and sponges shows phytotoxic and cytotoxic properties [103], 3,4-dihydroxybenzoic acid shows antioxidant properties and was already found in pygidial defensive glands of several dytis-cid beetles. 

Fig. 11. Schematic drawing of N-acetyl-tryptophan-methyl-amide (NATMA) showing the Ramachandran angles, (, ...

B. C. Dian, A. Longarte, S. Mercier, D. A. Evans, D. J. Wales, and T. S. Zwier (2002) The infrared and ultraviolet spectra of single conformations of methyl-capped dipeptides N-acetyl tryptophan amide and N-acetyl tryptophan methyl amide. J. Chem. Phys. 117, p. 10686... 

Scheme 21 Pd-catalyzed direct arylation of N-acetyl-tryptophan methyl ester.

Figure 11 shows the result of this experiment on a solution of 5 mM N-acetyl tryptophan and 0.2 mM 3-N-carboxy-methyl lumiflavin, hereafter simply called flavin (see Figure 10). Positive enhancements can be observed for the aromatic C-2, C-4 and C-6 protons, while the CH2 group shows emission. This polarization pattern corresponds with a tryptophyl radical in which the electron spin is delocalized over the aromatic ring. It can further be noted that almost no flavin polarization is present in the difference spectrum. Figure 11c (weak lines are present at 2.6 and 4.0 ppm). This is due to cancellation of recombination and escape polarization as will be discussed in Section 5. The mechanism of the photoreaction undoubtedly involves triplet flavin (17). Since 1-N-methyl tryptophan shows similar CIDNP effects, the primary step most probably is electron transfer to the photo-excited flavin. This is also supported by a flash photolysis study by Heelis and Phillips (18). The nature of the primary step in the photoreactions with amino acids is important in view of the interpretation of "accessibility" of an amino acid side chain in a protein as seen by the photo-CIDNP method. This question is therefore the subject of further study.

The Photo-reaction of Flavin with Tryptophan. Typical spectra obtained from the flavin/N-acetyl tryptophan (Trp) system in D2O are shown in Figure 17. At long delays (100 ms) the flavin peaks (labelled F) which were strong shortly after the laser flash have very nearly disappeared. In the corresponding spectrum obtained with c.w. laser illumination, (Figure 11) the flavin peaks are also very weak relative to those of tryptophan. Thus under steady state conditions a lot of information obtainable in a fast time resolved experiment is actually lost. As we shall see these effects are due to a rapid partial cancellation of geminate polarization. 

Figure 4. MHz H FT nmr spectra (10 pulses) of 5 x 10 N N-acetyl tryptophan and 2 x 10" M flavin I in D2O, pulse sequence of Figure 1, (a) light spectrum, (b) dark spectrum, (c) difference a-b.

Park YD, Rizzo TR, Peteanu LA, Levy DH (1986) Electronic spectroscopy of tryptophan analogs in supersonic jets - 3-indole acetic-acid, 3-indole propionic-acid, tryptamine, and N-acetyl tryptophan ethyl-ester. J Chem Phys 84(12) 6539-6549... 

Dian BC, Longarte A, Winter PR, Zwier TS (2004) The dynamics of conformational isomerization in flexible biomolecules. I. Hole-filling spectroscopy of N-acetyl tryptophan methyl amide and N-acetyl tryptophan amide. J Chem Phys 120 133... 

Shemesh D, Sobolewski AL, Domcke W (2010) Role of excited-state hydrogen detachment and hydrogen-transfer processes for the excited-state deactivation of an aromatic dipeptide N-acetyl tryptophan methyl amide. Phys Chem Chem Phys 12 4899... 

Heinrich et al. 167) studied the reaction of (132) with the model compound N-acetyl-tryptophan amide at a constant pH of 4.7. At least ten different reaction products could be detected some of them were expected on the basis of the results obtained by previous workers. However, in the case of N-acetyl-tryptophan amide, the most stable and abundant product was found to be a compound (134) bearing a 2-piperidone ring system, which could arise from a cyclization of the presumed intermediate (133) in the reaction. 

N-Acetyl-tryptophan and indole-3-propionic acid have been labelled with deuterium and tritium by Spande and Fontana 371), who employed the corresponding 2-sulfenyl derivatives. The spirolactones (176) obtained from (175) by treatment with N-bromosuccinimide were reduced with NaBD4 or NaBTa in good yields back to the corresponding indole compounds specifically labelled with deuterium or tritium at the 2-position. The method seems to offer a new general procedure which permits introduction of label specifically at the 2-position of indoles bearing a propionic acid side chain at the 3-position. 

Polyphosphate ester (PPE) is a good dehydrating agent in condensation reactions and is also a mild agent in some acid-catalyzed rearrangements 220, 454). N-Formyl- and N-acetyl-tryptophan and their esters were cyclized in the presence of PPE under mild conditions to to give the corresponding 3,4-dihydro-p-carboline-3-carboxylic acid derivatives (188) 220). 

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