THE PHENANTHRENE NUCLEUS129for acids containing substituents both on the side chainM-66-56and inthe nucleus.67In one instance the isolation of a small but significantamount of the isomeric 3,4-benzphenanthrene derivative arising from3,4-cyclization was reported.66Although cyclization of 7-2-phenan-thrylbutyric acids generally seems to favor the formation of the chrysenestructure, in the unsubstituted acid the ring may be induced to closeeither into the 3- or1-position,43depending upon the experimentalmethod used for cyclization (see p. 176). From this observation^ itappears that no valid generalization can be made regarding the propor-tion of isomers formed in any ring closure which ^has the inherent tend-ency to take place in two directions. A number of the following cycliza-tions fall into this category.The cyclization of /3-phenanthrylpropionic acids proceeded in twodirectionsawhen the acid side chain is located at the 1- or 9-position,
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