The facile synthesis of a series of tryptophan derivatives

Abstract

Further information on publisher's website:http://dx.doi.org/10. 1016/j.tetlet.2008.02.120 Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract-Tryptophan is an essential amino acid important as protein building block, for the anchoring and binding of membrane proteins, substrate in biosynthetic reactions, and as versatile label in protein folding and location studies. As fluorescent molecules, tryptophan derivatives are especially useful in the exact determination of 3-dimensional protein structure in solution and in bound states. This study reports a facile method to synthesise a variety of tryptophan derivatives that are difficult to prepare using alternative enzymatic approaches.

Mechanism for the direct synthesis of tryptophan from indole and serine: a useful NMR technique for the detection of a reactive intermediate in the reaction mixture

“…They also mentioned that N, O-diacetylserine (14) was obtained as a major product from the reaction of 2 and Ac 2 O, without the formation of 8. In contrast, in our NMR experiments, there is no evidence for the formation of 14 or intermediate 11: there are no signals other than those due to 6, 7, 8 and 9 in the reaction mixture of 6 with Ac 2 O-d 6 in AcOH-d 4 , even after 60 min, as shown in Fig. 2C.…”

“…Although all spectral data showed that our proposed mechanism is rational, Sanderson [4] proposed a different mechanism (Scheme 4). They concluded that the cationic species (11) derived from N,O-diacetylserine (14) is the key intermediate which is reactive in nucleophilic substitution reactions, and that 11 equilibrates to N-acetyldehydroalanine (8).…”

“…Yamada's group [3] applied this method to the synthesis of optically pure 7-bromotryptophan. Recently, Sanderson et al also reported [4] the synthesis of optically active tryptophan analogs having various substituents on the indole ring. However, the drawback of this reaction is the formation of racemers even if optically active L-serine is used.…”

“…It was reported [5] that the reaction of 8 with indole gave N-acetyltryptophane in 55% yield. In contrast, Sanderson proposed [4] another intermediate, cyclic oxonium ion (11), which is attacked by indole in an S N 2-type reaction.…”

The Suzuki–Miyaura Cross-Coupling as a Versatile Tool for Peptide Diversification and Cyclization

“…In contrast, the use of halotryptophans as substrates in Suzuki-Miyaura couplings was initially hampered by their limited commercial availability (NB: pseudohalogenated tryptophans and derivatization thereof have not been reported to date). Chemical synthesis of these building blocks often lack generality and require specific procedures for each regioisomer [70][71][72][73]. In view of this issue, a straightforward procedure for the enzymatic synthesis of halogenated tryptophans was described via use of tryptophan synthase on the corresponding readily available indole analogues [37,74].…”