Tetronic acid, hydroxy

Hydroxy-a,/3-alkynyl esters 28 in cyclic or acyclic form furnish 5,5-disubstituted tetronic acids (/ -hydroxy-a,/3-unsaturated-7-lactones) of type 29 in a simple one-pot procedure. At first, pyrrolidine is added as a base, and subsequent acid treatment effects lactonization to obtain the products in good yields (Scheme 35) <2006SL1607>. 

Butenolide, 2-hydroxy — see Isotetronic acids Butenolide, 3-hydroxy — see Tetronic acids But-2-enolide, 4-alkylidene-synthesis, 4, 697 Butenolides H NMR, 4, 578 mass spectrometry, 4, 585 structure, 4, 551 synthesis, 1, 416 trimethylsilylation... 

Effenberger and coworkers have utilized the tolerance of methyl ketones by the recombinant enzyme to develop an alternative synthesis of tetronic acids and their amino derivatives, as shown in Figure 5.18. Treatment of O-acyl cyanohydrins with lithium disilazide resulted in base-induced ring closure to amino tetronic acid derivatives. Alternatively, the cyanohydrins could be converted to a-hydroxy esters prior to acylation, and the same base-induced cyclization then led to tetronic acid derivatives [89]. 

In 1901 Anschutz suggested the denotation tetramic acid for 1,5-dihydro-4-hydroxy-2-pyrrololone 2a, a tautomer of 2,4-pyrrolidinedione la (09LA55). By analogy to the term tetronic acid, denoting the lactone of 4-hydroxy-3-oxo-butanoic acid (60QR292), tetramic acid is used to name the lactam of 4-amino-3-oxo-butanoic acid. (See Fig. 1.)... 

Carbonyldiimidazole can also function as a carbonyl equivalent (79TL4517). Condensation of the dianion derived from an a-hydroxy ketone (545) with this reagent provides a general although modest yield approach to tetronic acids (546 equation 7). 

Tetronic acids. N,N -Carbonyldiimidazole (1) can serve as an equivalent of C=0 in a synthesis of tetronic acids from dianions of a-hydroxy ketones or a -diketones. ... 

The simplest member (1) of the 2,3,4-furantriones is the one obtained by oxidizing the hydroxy tetronic acid (2) (Scheme 1). The interest in that ring system was increased after the discovery of L-ascorbic acid (3, vitamin C) and its oxidation product dehydro-L-ascorbic acid (DHA). The latter was formulated as the traditional compound 4, possessing the furantrione ring, but it was found to be equilibrated with other forms as will be discussed later. The role of 3 in biological systems arises from its function in the oxidation-reduction processes. The ratio of 3 with 4 may be related to cell division and therefore may have a critical role in growth regulation in addition to its use as antioxidant in foodstuffs. 

The importance of the bishydrazones of furantriones lies primarily in obtaining crystalline derivatives that are needed for their identification and to act as precursors for heterocyclic compounds. Thus, these materials can be traced back to the early work on hydroxy tetronic acid and vitamin C, where a number of the corresponding bishydrazones were prepared. 

Diketones (35) were needed to synthesise tetronic acids (34) and hence the natural products pulvinones. FGI on (35) gives -hydroxy ketones (36). These cannot be made by a benzoin condensation (Chapter 23) as the aldehyde required would enolise. The acyloin reaction in the presence of Me SiCI avoids this difficulty. 

Beilstein Handbook Reference) AI3-52393 2H-1-Benzopyran-2-one, 4-hydroxy- Benzo-tetronic acid BRN 0129768 Coumarin, 4-hydroxy- 4-Coumarinol EINECS 214-060-2 4-Hydroxycoumarin NSC 11889, Chemical intermediate. Crystals mp = 213-214 , GreeffR.W. Co. Janssen Chimica Penta Mfg,... 

Tetronic Acids. A synthesis of tetronic acids reported by Smith and co-workers relies on the reaction between (1) and the dianion derived from an a-hydroxy ketone (eq 8). The reaction proceeds in moderate yield (31-57%). 

To overcome this drawback the core structure of the molecules was modified. We switched to other cyclic ketoenol subclasses, e.g., tetronic acids, pyrazolidin-3,5-diones, 4-hydroxy-pyrones and 6-hydroxy-thiazinones. 

The action of ascorbic acid on many enzymes appears to be conditioned by other substances, notably metallic ions, present in reaction mixtures certainly where its action has been critically examined, this has been found to be so. Whether ascorbic acid in vivio has any regulatory influence on these enzymes is uncertain. Still more improbable is the view that this action of ascorbic acid constitutes one of its essential roles in the living cell, since it has been shown both for j3-amylase and urease that other dienols (reductone, dehydroxymaleic acid, reductic acid, hydroxy-tetronic acid) which are biologically inactive react similarly (Hanes, 1935 Mapson, 1946). 

No feeding experiments aimed at establishing the biosynthetic origin of the carbon atoms of TMN have been performed. Only a very limited number of studies performed on TSN or other antitumor antibiotic bearing tetronic acid moieties (4-hydroxy-[5//]furan-2-one) such as chlorothricin have been reported. Thus, the carbon skeleton of TSN is shown to consist of a polyketide chain derived from seven acetate units and six propionate units, combined with a C2 unit of unknown... 

Contents 0. R. GOTTLIEB, Neolignans - K. HERRMANN, Hydroxy-zimtsauren und Hydroxybenzoesauren enthaltende Naturstoffe in Pflan-zen - G. PATTEN DEN, Natural 4-Ylidenebutenolides and 4-Ylidene-tetronic Acids - R. D. H. MURRAY, Naturally Occurring Plant Coumarins - G. OHLOFF, Recent Developments in the Field of Naturally-Occurring Aroma Components - Author Index - Subject Index. 

Tetronic acids (4-hydroxy-2(5//)-furanones) are also an example of 5-membered rings, and they are compounds of potential activity as antibiotics, antiviral and neoplastic agents. The base-promoted Dieckmann condensation is one of the desired methods to produce 3-acyl-tetronic acids. An example is the intramolecular tetrabutylammonium fluoride-promoted Dieckmann cyclization of 53 to give tetronasin (54) in 72% yield. 

Tetronic Acids.—a-Alkoxytetronic acids (and ultimately a,a -dihydroxy-ketones) can be obtained from a-hydroxy-acids by condensation with a-bromo-alkanoyl chlorides to give lactides which undergo base-induced ring contraction (Scheme 19). °"... 

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