Abstract
Most of polypeptides containing α,β-dehydroamino acids have important biological activity, so exploration of synthetic method has practical significance. In this paper, dipeptides were prepared from l-threonine by protecting of c-terminal allyl acetate, and condensing reaction with a series of N-Boc amino acid. Then, treatment of dipeptides obtained with DMAP, (Boc)2O and tetramethylguanidine in the acetonitrile occured β-elimination reaction to yield stereoselectively dehydrodipeptides. Structures of dehydrodipeptides were confirmed by 1H NMR, 13C NMR and MS. Analysis of 1H NMR, 2D NMR and crystal structure showed that the dehydrodipeptides were Z-configuration.Graphical abstractDehydrodipeptides were prepared from l-threonine. Their structures were confirmed by 1H NMR, 13C NMR and MSElectronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-2005-z) contains supplementary material, which is available to authorized users.
Highlights
Most of polypeptides containing α,β-dehydroamino acids have important biological activity, so exploration of synthetic method has practical significance
Dipeptides were prepared from two amino acid, dehydrodipeptides were obtained by β elimination dehydration of dipeptides
If l-threonine was treated with allyl bromide in dry DMF, besides carboxyl group, the amino group was reacted with allyl bromide
Summary
Synthesis In the synthesis of dehydrodipeptides, first, we obtained dehydroamino acids using N-protected β-hydroxyamino acid esters as raw material. Of (Boc)2O in the presence of DMAP, gave O-tertbutyl carbonates of dipeptides, followed by direct reaction with N,N,N,N-tetra-methylguanidin (TMG) without isolation, afforded the corresponding dehydrodipeptides in good yields. This two-step method can be carried out as a one-pot procedure. In comparison with previous methods, this procedure is a onestep process, since separation of the intermediates is unnecessary and theatment of intermediates with TMG gave the corresponding dehydrodipeptides in good yield This mildness of the mothod is compatible with the presence of a variety of functional groups. X-ray crystallographic analysis of 6c reveals that the double bond C7–C8 in dehydrodipeptides was Z
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