Acid anhydrides contributing structures

The gross structural features, presence of a tetramic acid and E-decenoyl side chain, could be inferred from NMR studies. Methanolysis (HCl/MeOH) of 47 and pentane extraction of the quenched reaction mixture gave two compounds that were determined to be the methyl esters of decenoic acid and N-(2-decenoyl)leucine. The nature of the 3-acyl tetramic acid was deduced from the identification of 48 and 49 in the aqueous portion of the methanolysis reaction mixture following treatment with trifluoroacetic acid anhydride. The unusual C-C bond fragmentation under acidic conditions, and the structure of the antibiotic was confirmed by synthesis of racemic 47 [86]. The configuration at the lone chiral centre was established as R by chiral GC. The carbon NMR spectrum of 47 indicated an equilibrium between three tautomers in which the A2-pyrrolin-4-one form is preferred (60%) and the two internal tautomers (50, 51) make equal contributions (20% each). 

The same group has investigated the photo-addition of alkenes to 1,2- and 2,3-naphthalenedicarboxylic acid anhydride.No products of addition of the alkene to the naphthalene ring were observed instead the alkene inserts into the C(=0)-0 bond of the anhydride or adds to one of the carbonyl groups to produce an oxetane. By analogy with imides, the insertion reaction can be viewed as an addition to the partial C-o double bond Illustrated by the contributing structure (81) to give adduct (82) which collapses to the isolated insertion product (83). 

The name of this structural class ( quinoline ) in the Colour Index is not ideal because quinoline derivatives feature in other related classes, such as the methine basic dyes with a quinolinium cationic group. The class is more precisely associated with quinophthalone (1.15), the characteristic chromogen derived by condensation of quinoline derivatives with phthalic anhydride. This small class of yellow compounds contributes to the disperse, acid, basic and solvent ranges of dyes. 

Other defects that may occur in polyAN include acrylamide (10) and acrylic acid (11) units, resulting from adventitious hydrolysis of AN units, and also derived cyclic structures such as anhydrides (12), imino-amides (13) and imino-esters (14). These structures give rise to characteristic additional peaks in the and NMR spectra of the polymer and they also contribute to the purely aliphatic regions of the spectra [68-70]. 

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