Strain energies of the hydrocarbons derived from the fragments of C , , along the C5, C, and C, symmetry pathways indicate that the strain energy per carbon (E,) increases gradually along the C, and C2paths, but has a maximum at C, , H, , along the C, path. C,,-Sumanene, 10, has been recognised as a leading fragment along C, route with an inversion barrier of 24.2 kcal mol-' and a bowl depth of 1.15 A at M N D O level. This contrasts with C,,-corannulene, 6, which is a more shallow bowl with a lower inversion barrier. The bond alternation in the central six membered ring of sumanene resembles that of C6, . The higher fragments en route t o C , are deep bowls with higher barriers for inversion. A n approach to sumanene via a triphenylene derivative, 26, has been probed and an increase in strain through sequential placement of methylene bridges has been estimated, using M N D O and MM2 calculations. Synthetic routes t o a doubly bridged triphenylene, 28, and schemes for further elaboration of 26a and sumanene derivative, 29, towards C , , are considered.Note added in prooj after this paper had been submitted, Dr. Andre Rassat sent us a reprint of his paper (C. Fabre and A. Rassat, C. R. Acad. Sci. Paris, Ser. 2. 1989, 1223) which is relevant to this study. We thank Dr. Rassat for the reprint.