- Synthesis of tripeptides containing d-Trp substituted at the indole ring, assessment of opioid receptor binding and in vivo central antinociception
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The noncationizable tripeptide Ac-d-Trp-Phe-GlyNH2 was recently proposed as a novel minimal recognition motif for μ-opioid receptor. The introduction of different substituents (methyl, halogens, nitro, etc.) at the indole of d-Trp significantly influenced receptor affinities and resulted in serum stability and in a measurable effect on central antinociception in mice after ip administration.
- De Marco, Rossella,Bedini, Andrea,Spampinato, Santi,Gentilucci, Luca
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supporting information
p. 6861 - 6866
(2014/10/15)
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- Regioselective enzymatic halogenation of substituted tryptophan derivatives using the FAD-dependent halogenase RebH
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Regioselective methods to establish carbon-halide bonds are still rare, although halogenation is considered as a commonly used methodology for the functionalization of organic compounds. The incorporation of halogen substituents by organic synthesis usually requires hazardous conditions, shows poor regioselectivity and results in the formation of unwanted byproducts. In addition, halogenation by electrophilic aromatic substitution (SEAr) obeys distinct rules depending on electron-withdrawing or -donating groups already present in the aromatic ring. We employed the tryptophan-7-halogenase RebH for regioselective enzymatic halogenation to overcome these limitations. In combination with a tryptophan synthase, an array of C5- and C6-substituted tryptophan derivatives was synthesized and halogenated by RebH. The halogenase is able override these directing effects and halogenates at the electronically unfavored C7-meta-position, even in presence of ortho/para-directing groups. No business as usual: The tryptophan halogenase RebH from Lechevalieria aerocolonigenes is able to halogenate at the electronically unfavored C7-meta-position of C5-substituted tryptophan derivatives, even in presence of deactivating ortho/para-directing groups.
- Frese, Marcel,Guzowska, Paulina H.,Voss, Hauke,Sewald, Norbert
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p. 1270 - 1276
(2014/05/20)
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- The facile synthesis of a series of tryptophan derivatives
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This study reports a facile method for the synthesis of a variety of 5- and 6-substituted tryptophan derivatives that are difficult to prepare using alternative enzymatic approaches. Acylation of an activated amino acid, derived from serine in situ, is coupled with an enzymatic resolution step to furnish enantiopure analogues bearing a range of electron withdrawing and releasing substituents. Isolation of a dehydroalanine derivative as a by-product from some reactions provides some insights into the likely mechanism of the reaction.
- Blaser, Georg,Sanderson, John M.,Batsanov, Andrei S.,Howard, Judith A.K.
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p. 2795 - 2798
(2008/09/19)
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