Ester linkages of p-coumaric acid

Nakamura Y, Higuchi T (1976) Ester linkage of p-coumaric acid in bamboo lignin Holzforschung 30 187-191... 

Shimada M, Fukuzuka T, Higuchi T (1971) Ester linkages of p-coumaric acid in bamboo and grass lignins. Tappi 54 72-78... 

Nakamura, Y, and Higuchi, T. (1978) Ester linkage of p-coumaric acid in bamboo lignin. II. Syntheses of coniferyl p-hydroxyhenzoate and coniferyl p-coumarate as possible precursors of aromatic acid esters in lignin. Cellul. Chem. Technol. 12(2), 199-208. 

Benzaldehydes (lg, 2g, 3g) are liberated in the same way but originate in part from other sources (cf. Fig. 6.1.2). The presence of benzoic acids (lh, 2h, 3h) and ferulic acid (1 j) can be explained by hydrolysis of ether or ester linkages. p-Flydroxybenzoic and p-coumaric acids (3h and 3j, respectively) are attached to certain types of lignins by ester linkages and their occurrence in the acidolysis mixtures is, in these cases, at least primarily due to the hydrolysis of these linkages. 

Dimers 39 and 40, issued from grass samples, reveal the linkage type of p-cou-maric and ferulic esters and show that some ester bonds survive thioacidolysis. Dimer 39 confirms thatp-coumaric acid is ester-linked at Cy of S lignin units [60,61]. Compound 40, tentatively assigned from its mass spectral fragmentation pattern, may originate from ferulic units ester-linked to pentose units [85]. 

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