CHEMISTRY OF UNIQUE CHIRAL OLEFINS .3. SYNTHESIS AND ABSOLUTE STEREOCHEMISTRY OF 4'-OCTAHYDRO-3,3'-DIMETHYL-4,4'-BIPHENANTHRYLIDENE AND 4'-OCTAHYDRO-3,3'-DIMETHYL-4,4'-BIPHENANTHRYLIDENE

Unique chiral olefins with two methyl groups as the internal reference of absolute stereochemistry, 4'-octahydro-3,3'-dimethyl-4,4'-biphenan thrylidene (3) and its (3R,3'R)-(P,P)-(Z)-isomer (4), were synthesized in optically pure form starting from R)-(+)-1,2,3,4-tetrahydro-3-meth yl-4-phenanthrenol (11), which was obtained by the enantioresolution u sing a novel chiral auxiliary of dichlorophthalic acid amide (14). The absolute stereochemistry of chiral trans-dimethyl olefin (-)-3 was de termined by the X-ray crystallographic analyses of ester (-)-16b and ( -)-3 itself. Optically pure cis-dimethyl olefin 4 was prepared by phot ochemical reaction of trans-olefin (-)-3. The CD spectra of these chir al dimethyl olefins exhibit very intense Cotton effects in the B-1(b) transition region reflecting their strongly twisted pi-electron system s. The CD spectrum of (3R,3'R)-(P,P)-(E)-((-))-3 is almost similar in shape but opposite in sign to that of ',2,2',3,3',4,4'-octahydro-4,4'- biphenanthrylidene (1). Therefore, the absolute stereochemistry of (M, M)-(E)-1 previously theoretically determined was established in an exp erimental manner. The CD spectrum of (3R,3'R)-(P,P)-(Z)-4 is also almo st similar in shape but opposite in sign to that of ',2,2',3,3',4,4'-o ctahydro-4,4'-biphenanthrylidene (2). The absolute stereochemistry of (M,M)-(Z)-2 theoretically determined was corroborated.