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Three diastereomers of 3,3′-di-t-butyl-1,1′-spirobi[benz[e]indan], (lS,3R,3′R)-(1a), (1S,3S,3′S)-(1b), and (1S,3R,3′S)-(1c), have been prepared; c.d. spectral evidence is presented for their different conformations.

The absolute configuration of (-)-1,5-disubstituted 9,10-dihydro-9,10- etheno-or -ethano-anthracenes as indicated by c.d. spectral analysis are not consistent with those determined by the current X-ray method; this work provides an additional example to the accumulated results that the rigorous exciton theoretical analysis of c.d. spectra does not agree with the Bijvoet method of X-ray crystal analysis.

1,6,12,17-Tetra-t-butyl-2,4,13,15-tetradehydro[22]annulene has been synthesized and shown to be aromatic and to have fairly high conformational stability by n.m.r. spectroscopy.

The absolute configuration of (+)-1,5-dicarboxy-9,10-dihydro-9,10- ethenoanthracene (IV) was shown to be 9R,10R by chemical correlation with (-)-2,5-diacetoxy-7-carboxytriptycene (V) whose configuration was proved to be 1S,6R by X-ray analysis by the Bijvoet method combined with chemical correlation.

The synthesis of aromatic 3,11,14,22-tetra-t-butyl-1,12-didehydro[22]annulene by reductive dehydroxylation of cyclodocosaoctaenediynediol is described.