Tetronic acids formation

It is assumed that in the formation of 2-509, a Knoevenagel condensation of the benzaldehydes 2-511 and tetronic acid 2-512 initially takes place, and this is followed by the generation of a hemiaminal with the aniline 2-510 and an electrophilic substitution. 

The reaction of a nitrile with a Reformatsky reagent is known as the Blaise reaction and when applied to (9-trimethylsilyl cyanohydrins leads to the formation of tetronic acids with high ee [79]. By working-up the Blaise reaction with ammonium chloride it is possible to isolate... 

The O-antigens of Brucella species are homopolymers of a-l,2-linked 4,6-dideoxy-4-formamido-D-mannopyranose residues in which there may bea-1,3 linkages [102,103], The Yersinia 0 9 antigen is a similar 1,2-linked homopolymer but contains no 1,3 linkages. A related structure Y-acylated by 3-deoxy-L-glycero-tetronic acid in place of the formate group is produced by Vibrio cholerae Inaba and Ogawa strains [104], These structures have been the subject of synthetic work [105-107],... 

Figure 6 Formation of tetronic acids from B-ether type of structures by ozonation.

Three-components reaction of an aldehyde, enamine 31 and tetronic acid 310 in glacial acetic acid under MW irradiation without a catalyst gave the furoquinolines 309 (06S3874), via the formation of the arylidene derivative 311 (Scheme 58). 

Bentley, R., and J. G. Keil Tetronic Acid Biosynthesis in Molds II. Formation of Penicillic Acid in Penicillium cyclopium. J. Biol. Chem. 237, 867 (1962). 

In 2006, be Gall et al. [67] presented a conceptually different approach for the synthesis of pulvinic acids, starting from commercial tetronic acid 87 (Scheme 1.12). The protocol involves application of Pattenden s arylidenylation by aroyl formates, iodination, and aryl coupling by Suzuki reaction. The utility of be Gall s method was exemplified by the synthesis of vulpinic (24) and pinastric (26) acid. 

The complete enolization of tetronic acids is common. Double enolization with formation of the 2,4-dihydroxyfuran system occurs only in cases of strong stabilization by hydrogen bridges (59). 

Pelter and Al-Bayati developed tetronic acid derivative 175 as a synthon for a variety of butenolide derivatives, particularly those substituted at C(5). Reaction of 175 with maleic anhydride produced 177 in 80% yield, presumably through the intermediacy of cycloadduct 176 (Scheme 13.44) [80]. No stereochemical details were reported. Chemists at Monsanto, who were looking for a synthetic route to oxygenated aromatics, examined the similar tetronate derivative 179, available by silylation of 178. Reaction of 179 with DMAD followed by an aqueous HCl workup provided hydroquinone 180 in 70% yield [80]. Interestingly, reaction of 179 with either maleic anhydride, ethyl acrylate, 2-chloroacrylonitrile, or 1,4-naphthoquinone followed by exposure of the crude cycloadduct to aqueous HCl remmed to dienophUe and 178. NMR analysis of the reaction mixtures support the formation of the oxabicyclic Diels-Alder adducts. The authors suggested that the acid serves to remove the trimethylsilyl group and promote a cycloreversion reaction that is driven by the relief of strain. 

Pteridine-2-sulfonic acid, 4-oxo-3,4-dihydro-synthesis, 3, 300 Pteridine-2,4,6,7-tetrone formation, 3, 308 reactions, 3, 296 synthesis, 3, 291... 

It can be prepared by treatment of 3-amino-2//-azirines (e.g. 3-(dimethyl-amino)-2,2-dimethyl-2//-azirine) with an amino acid or peptide and, finally, with a (u-hydroxyacid. The formation of the oxazolone, VI/121, is observed when VI/120 is treated with acid. The ring enlargement step, the conversion of VI/121 to VI/122, is observed under the same conditions. The transformation of (-)-(R,R)2- 2-[2-(2-hydroxy-2-phenylacetamido)-2-methylpropionato]-2-phenylacetamido -N,N,2-trimethylpropionamide (VI/123) to (-)-(R,R)-3,3,9,9-tetramethyl-6,12-diphenyl-l,7-dioxa-4,10-diazacyclododecane-2,5,8,ll-tetrone (VI/126) in dry toluene/hydrochloric acid at 100° was observed in a 88 % yield. Compounds VI/124 and VI/125 are discussed to be intermediates. In an analogous reaction sequence cyclopeptides can be synthesized [93]. 

---