Metal-Catalyzed and Metal-Mediated Approaches to the Synthesis and Functionalization of Tetramic Acids

Abstract

The heterocyclic ring of tetramic acids is found in naturally occurred biologically active products isolated from fungi, bacteria, molds, and sponges. Thus, these molecules have attracted significant attention as synthetic targets, and various synthetic paths have been developed. Over recent years, a growing number of catalytic approaches toward functionalized products have been established in order to overcome the limitations of the conventional methods. The present review describes the strategies for the metal-catalyzed and metal-promoted synthesis and further derivatization of tetramic acids, with emphasis on recent examples from the literature.

Mediation of metal chelation in cysteine-derived tetramate systems

“…3 and Scheme 4), as supported by HMBC analysis (Fig. S2, ESI †) and by comparison of carbonyl 13 C NMR peaks with earlier reports. 29 They were also a single diastereomer at C-2/C-5 with characteristic and consistent H-2 chemical shis (Table S4, ESI †).…”

“…10 However, while some tetramic acids demonstrated increased toxicity as a metal complex, 11 in others, toxicity was attenuated by metal chelation. 12 Naturally occurring 3-acyltetramates have been reported to chelate a wide variety of metals, [6][7][8]13,14 including most commonly Cu(II), [15][16][17] Mg(II), Ca(II), 11 Fe(III) and Ni(II), 17 but also Zn(II), Ga(III), La(III), Ru(II), 9 Al(III), 18 Pd(II), 19 Co(II), 20 Rh(I), 21 Na(I), K(I), 22 Cs(I), 23 Cd(II), 24 Pb(II), 25 Ba(II), 26 Hg(II), 27 and Mn(II). 28 X-ray photoelectron Fig.…”

Functionalised bicyclic tetramates derived from cysteine as antibacterial agents

“…Tetramates are of interest 1-4 principally for their antibacterial activity, 5,6 and we have reported recently that systems derived from the amino acids, serine 1a, 7 threonine 1b, 8 and cysteine 1c 9 provide useful templates for application in synthetic and medicinal chemistry, which in some cases exhibit potent antibacterial activity. Amongst various methodologies to these derivatives, 10 our route makes use of the preferential formation of the malonamides of t-butyl oxazolidine/thiazolidine templates, formed as the cis-2,5-isomer 2a-c rather than the alternative trans-2,5-3a-c, which mimises the steric Table 1 5 5 a Major form is tautomer pair AB -see Figure 4 and Table 2.…”

α-Functionally Substituted α,β-Unsaturated Aldehydes as Fine Chemicals Reagents: Synthesis and Application

“…Subsequent oxidation of 11 with 2-iodoxybenzoic acid (IBA) in DMSO at room temperature affords 2-alkenal 12 in high yield (99%). It should be underlined that aldehyde 12 is an important building block in the synthesis of 3,5-unsubstituted 4- O -alkyl tetramates (versatile starting compounds for design of a wide variety of natural products and analogues) [ 22 , 23 ].…”