Dihydrocinnamic acid ester

A representative synthesis of the dihydrocinnamic acid ester (shown in Scheme B) begins with the bromination of vanillin (8). 

Charlton [57] demonstrated the use of oxazolidinones as effective chiral auxiliaries the commercially available (4i )-benzyl and (4S)-isopropyl-2-oxazolidinones were /V-acylated with dihydrocinnamic acid to give N-acyloxazolidinones (54 and 55) in yields greater than 80%, Scheme (10). Diastereoselective alkylation with tert-butylbromoacetate gave in each case principally only one diastereomer (56 and 57, respectively) (de>95%). The oxazolidinone moiety could be removed by utilizing LiOH-H2C>2 without affecting the tert-butyl ester. The crude acid was reduced to the corresponding primary alcohol with BH3THF, then... 

Polymeric Evans auxiliary 76 was also applied to aldol reactions2 4 (Scheme 1.6.37). In a model reaction, immobilised dihydrocinnamic acid was converted into the boron enolate and reacted with isovaleraldehyde. Products were released by treatment of the resin with NaOMe. The p-hydroxy ester 79 was obtained in a 20 1 diasteromeric ratio, along with some ester 80 derived from unreacted starting material. 

Cinnamic (1), p-coumaric (2), and related acids may be activated by conversion to CoA esters by CoA ligases [e.g., 4-coumarate CoA ligase (EC 6.2.1.12)] in much the same way that fatty acids are activated. The reduction of the CoA esters of cinnamic acids to cinnamyl alcohols involves two enz)mies cinnamoyl-CoA oxidoreductase (which forms the aldehydes) and cinnamyl alcohol dehydrogenase (Grisebach, 1981). Phenylpropanoids appear to be synthesized from the CoA esters of this series of acids by conversion to the corresponding aldehydes, then to the alcohols, and finally, by elimination of a phosphate group, to allyl and propenyl compounds. In many plants, mixtures of all t3q>es co-occur (Fig. 8.7) (Gross, 1981 Mann, 1987). Reduction of the side chain to produce dihydrocinnamic acids and related compounds is also known to occur in nature. 

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