4-epidehydroabietic acid

Pinus monticola. Further studies on the oleoresin of the white cypress, Callitris columellaris, show that it contains cis- and trans-communic acids, communic acid, sandaracopimaric acid, and 7-oxo-4-epidehydroabietic acid. Dundathic acid is a polymer of communic acid containing ca. four diterpenoid units. 

Callitrisic acid (4-epidehydroabietic acid) has been synthesized from podo-carpic acid. After insertion of the isopropyl group, the phenolic hydroxy-group... 

We first think about the different reactivities of axial and equatorial isomers through the examples shown in Figure 1.10. Esters 12 and 13 are called methyl 4-epidehydroabietate (12) and methyl dehy-droabietate (13). Dehydroabietic acid can be esterified with methanol and sulfuric acid to give 13, while 4-epidehydroabietic acid cannot be esterified under the same conditions. Ester 12 can be prepared only through methylation with diazomethane. Although ester 13 can be hydrolysed with sodium hydroxide in methanol, the stereoisomer 12 cannot be hydrolysed under the same conditions. This reduced reactivity... 

The mixture of olefins obtained by lead tetra-acetate decarboxylation of 4-epidehydroabietic acid is very nearly the same as from dehydroabietic acid. Isomerization of these 19-nor-tetra-enes led to some products with a cis a/b ring... 

---