Structures of Reported Compounds

In Table 2, diterpene structures are identified by compound number and grouped with related structures belonging to the same skeletal type. The structural 

Double bonds are always indicated by a two-center code (e.g., 3(4), 9(11)) that identifies the two carbons linked by the double bond. If double bonds occur within the ring system, the steric relations around the double bond are defined by the skeleton illustrated with the description. Thus, for each cyclic double bond the steric relationship (Z or E) of the ring carbons attached to the doubly bonded carbons is defined by the relationship indicated in the illustrated skeleton. 

For linear diterpenes or the linear segments of cyclic compounds with ambiguous double bond stereochemistries, the steric relationship about the double bond is indicated by a Z or E suffix (e.g., 13(14)E, 2(3)Z). The Z or E assignment results from the comparison of the sequence-rule-preference of the four atoms attached to the doubly bonded carbons (as specified in Rule E-2.2. of the lUPAC Rules for Nomenclature of Organic Chemistry). Several examples of Z and E assignment are discussed below in order to familiarize the reader with this method. 

Ketones and Aldehydes Ketones and aldehydes are denoted by the carbonyl group code, (=0), associated with a secondary (ketone) or primary (aldehyde) carbon of the skeleton (e.g. 3(=0)). 

Epoxides, Ether- or Oxido-Linkages, etc. Epoxides and other oxido-bridges are indicated by a code (e.g. 3/3(—O—)4/3) specifying the two centers of attachment and, if known, the orientivity of attachment. 

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