Triones specificity

An acid-catalyzed substitution of a 6-oxo group on 2-aminopteridine-4,6-dione with hydrogen chloride in alcohols (65-100°, 3 hr, 80% yield) represents a convenient synthesis of the 6-alkoxy analogs. The reaction proceeds also with pteridine-2,4,6-trione and its 1-methyl and 1,3-dimethyl derivatives. While methoxylation of 2,4,7-trichloro-quinoline gives about equal amounts of 2- and 4-substitution, acid-catalyzed hydrolysis gives specific reaction at the 2-position only. ... 

Regiospeciflcity combined with diastereotopic face specificity is seen in the reduction of the trione (60) to (61) (Scheme 26). ° In Scheme 27 the reduction is quite regiospeciflc, but both diastereotopic feces of the exocyclic ketone function of (62) are attacked to give the erythro-(63) and threo- 64) hydroxy ketone products. The degree to which regio specificity and diastereotopic face specificity can be controlled with different enzymes is shown in the bile acid reductions of Scheme 28. ° ... 

The simpler nitrogenous constituents of wort consist principally of a-amino acids which can be estimated by the colour reaction either with indane-1,2, 3-trione hydrate (ninhydrin) or 2,4,6-trinitrobenzenesulphonic acid. With ninhydrin, a-amino acids develop a violet colour which can be measured at 570 nm while proline, an important imino acid in wort and beer, gives a yellow colour measured at 440 nm. 2,4,6-Trinitrobenzenesulphonic acid is more specific, for amino acids and does not react with proline or ammonia. It forms yellow derivatives which can be estimated colorimetrically at 340 nm. 

Specifically, an efficient protocol to afford 2//-indazolo[2,l-fc]phthalazine-l,6,ll(13H)-triones (10) from a condensation reaction of phthalhydrazide (11), 5,5-dimethyl-l,3-cyclohexanedione (12) (dimedone), and aromatic aldehydes was studied (Scheme 1.7). 

J.M. Khurana, A. Lumb, A. Chaudhary, B. Nand, Efficient and green synthesis of 12-aryl-2A4,12-tetrahydrobenzo[6] xanthene-l,6,ll-triones in water and task-specific ionic liquid, Syn. Commun. 43 (2013) 2147-2154. 

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