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Enaminones were prepared from b-ketoesters or 1,3-diketones and primary amines in water as solvent Enaminones and related compounds possessing the structural unit N-C=C-Z (Z = COR, CO 2 R, CN, etc.) are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. 1 Some procedures reported for the synthesis of b-enaminocarbonyl derivatives include the reaction of amines and 1,3-diketones supported over clay K 10 /ultra-sound 2 or silica under microwave irradiation, 3 reaction of b-amino ketones in the presence of triethylamine promoted by Pd(II), 4 and reactions of a-metalated imines with esters. 5 However, the generally employed method for the preparation entails the reaction between ammonia or a primary or secondary amine with 1,3-dicarbonyl compound in benzene solution with azeotropic removal of the water formed. [6][7][8][9][10] We report here, a simple procedure for the synthesis of benamino esters and enaminoketones (1) starting from bketoesters or 1,3-diketones and primary amines in water as solvent (Scheme 1). The main advantages of this methodology are: (a) the reaction is simple to perform; (b) the reaction occurs at room temperature; (c) the yields are good to high, (d) acid catalysis is not necessary, (e) the reaction works for a variety of primary amines; and (f) purification of the enaminones is not necessary. With secondary amines or simple carbonyl compounds, no reaction was observed. The reaction worked very well to soluble amines, but with less soluble amines the yield was moderated and it was necessary to use high excess of amine (3 equivalents). When b-ketoester and 1,3-diketones reacted with ethylene-diamine, diaminones were observed as products (1h and 1m). Scheme 1Since there are two carbonyl groups in the starting material and 2 equivalents of amine were added, there should be several products in this reaction, i.e., the amine may react with one or both of carbonyl groups. Thus, there should be three products from b-ketoester and two from 1,3-diketone, however, only enaminones were observed as products. This probably occurs because the acetyl portion of the starting dicarbonyl compounds is more reactive than the ester or aromatic conjugated carbonyl. When the enaminone is formed, it is stabilized by resonance, blocking the formation of other products. The conjugation effect also justifies the formation of only one product from acetylacetone.The probable explanation for the formation of enaminones in water is their tautomeric forms (A and B) associated with the hydrogen bond. 11,12 Enaminones of all types exist predominantly in the carbonyl form and are stabilized by the contribution of the zwitterionic form (C), 13 which can be solvated by water preventing hydrolysis of the formed enaminone. This explanation can be supported by the fact that no reaction was observed using secondary amines or simple carbonyl compounds (Scheme 2). Scheme 2In summary, we have provided a remarkably viable alternative route for the synthesi...

The method proved to be simple, rapid and useful to estimate administered doses for further pharmacological and toxicological investigations of ayahuasca exposure.

Microcystins (MC) are a family of hepatotoxic cyclic heptapeptides produced by a number of different cyanobacterial species. Considering the recent advances in the characterization of deprotonated peptides by mass spectrometry, the fragmentation behavior of four structurally related microcystin compounds was investigated using collision-induced dissociation (CID) experiments on an orbitrap mass spectrometer. It is demonstrated in this study that significant structural information can be obtained from the CID spectra of deprotonated microcystins. A predominant ring-opening reaction at the isoMeAsp residue, as well as two major complementary fragmentation pathways, was observed, reducing the complexity of the product ion spectra in comparison with spectra observed from protonated species. This proposed fragmentation behavior was applied to characterize [Leu(1)]MC-LR from a cyanobacterial cell extract. In conclusion, CID spectra of microcystins in the negative ion mode provide rich structurally informative mass spectra which greatly enhance confidence in structural assignments, in particular when combined with complementary positive ion CID spectra.