Enolones

Bolasterone Ethylestrenol Fluoxymesterone Metenolone Acetate Methandros t enolone Nandrolone... 

As a further illustration of the phenomenon of H-bond resonance coupling let us consider the intramolecular H-bond of (3-hydroxyacrolein (0=CHCH=CH0H), a prototypical enolone (2-en-3-ol-l-one, or enol isomer of (3-diketone).55 This molecule may be envisioned as existing in two distinct isomeric forms, according to the position of the proton in the O- H—O hydrogen bond ... 

The photochemically induced radical addition of alcohols to enones has been described by Fraser-Reid [104-109]. Here again, the sense of addition depends on the steric effects of substituents, attack anti to the C-5 substituent being preferred [108,110]. Other uses of sugar-derived enones to trap radicals have been reported [111]. Enolone 77 gave interesting results in terms of selectivity [112]. In this instance, radical addition occurs with an equatorial selectivity, whereas cuprate addition occurs with an axial selectivity [9,62]. 

F. W. Lichlenthaler, Sugar enolones Synthesis, reactions of preparative interest and y-pyrone formation, Pure Appl. Chem. 50 1343 (1978). 

B. Giese and T. Witzel, Stereoselective radical reactions with enolones, Tetrahedron Lett. 28 2571 (1987). 

Photobromination of the enolone 69 is of interest, because radicals formed at C-1 or C-5 (carbohydrate numbering) are both subject to captoda-... 

In this context, pyranoid sugar enolones of type 8, or 9, i. e. those that carry chiral centers on either side of the enolone structural element, are even more powerful building blocks stereoselectivities in addition reactions. They are accessible in various substituted forms from the respective hydroxyglycal esters in another, preparatively delightful reaction channel, a chlorination - hydrolysis elimination sequence (27, 28). 

Indeed, the insight into the intricate stereochemical details of ensuing reactions of the pyranoid enolone ester bromide 3 - the pyranoid enolone ester 14, de facto, is an actinospectoside derivative, 16 a structural element of the spectinomycin as well as uscharidine-type cardiac glycosides (except for the terminal benzoyloxy group) - eventually led to practical synthetic strategies for their acquisition. 

The versatility of the enolone ester 27 is illustrated by a variety of synthetically useful addition reactions, e. g. with lithium alkyls, Grignard reagents and cyclopentadiene in a Diels-Alder type fashion (40, 48, 49), but, most notably, it could be utilized for straightforward syntheses of the marine natural products (-)-bissetone (28), a metabolite from the Gorgonian soft coral Briareum polyanthes (50), and (-)-palythazine (29), an unusual dipyranopyrazine isolated from the salt water invertebrate Palythoa tuberculosa (51). 

An Isolation and concentration scheme should be appropriate for the sample under Investigation. As an example of this, a distillation technique would not be satisfactory for separating caramel aroma compounds such as Maltol, Cyclotene, or Furaneol which possess an enolone structure and do not steam distil. 

Roasting conditions (blend I = medium and blend II = dark roast) influence the spectrum of furans and reductones considerably. Reactive aldehydes and enolones decrease and furfurylalcohol, furancarboxylic acid and Maltol increase significantly. Components 1 to 5. are formed via 3-deoxy- and S to JJ via 1-deoxyosones. In addition, caramelization may also be involved. 

Thus, Tressl et al.219 characterised eight 2-(l-pyrrolidinyl)-2-cyclopentenones and 11 cyclopcnt(/ )azcpin-8( lf/)-oncs from proline-monosaccharide and proline-cyclic enolone systems. The compounds possessed bitter tastes, with the former exhibiting concomitant astringency. The bitter thresholds in water of Structure 33 and 34 were 50 and 10 ppm, respectively. 

Carbohydrate-derived enolones are a particular case of chiral cyclohexenes. Addition of tert-butyl radicals occurs with high stereoselectivity trans to the C-5 substituent at both x- and /f-anomers8I5. The primary adduct radical rearranges through transfer of the benzoyl group and final hydrogen atom abstraction to yield the product as a mixture of isomers at C-2. Treatment of the mixture with pyridine leads to the formation of one enolone wdth elimination of benzoic acid. 

Dihydropyranones 5 containing an enolone ester function reacts with cyclopentadiene (6) under thermal, high-pressure and Lewis acid conditions12. Generally, high-pressure and Lewis add mediated cycloadditions are shown to be the most useful in terms of the degree of selectivity and overall yield. 

An extensive (re)investigation of the additions of IN3, Br2 and Br2/MeOH to tri-0-acetyl-D-glucaI and tri-O-benzyl-D-galactal has been reported. The results are in keeping with previous knowledge. The enolone 3 when treated with... 

A related rearrangement of the enolone (13) gave the unsaturated C-glycoslde derivative (l4) in yield (Scheme 7), and prolonged treatment of tetra-O-acetyl-2-hydroxy-D-glucal or -galactal with... 

Glycosid-2-ulose derivatives mesylated at 0- 1 give access to enolones, e.g. (1), from which glycosid-3-ulose compounds, e,g. 

The unusual enolone unit (43) has been found as a component of a... 

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