CPL spectra in THF. Due to similar helical backbones, all systems showed similar
Cotton effects with strong negative Cotton effects at ~290 nm and positive ones
at 315–320 nm for the (P)-(+)-55a-e,56 enantiomers. The g abs values were
found within the range of +2.63 Â 10
À3 to +4.77 Â 10
À3 for the (P) enantiomers
Fig. 4.19 Chemical structures, fluorescence, and CPL activity of pentahelicenic (P)-23 and of D 3 -
symmetric triple pentahelicene (P,P,P)-54. Adapted with permission [53]. Copyright 2018, American Chemical Society
Ph
Ph
OH
OH
OH
OH
R 2
R 2
(P)-(-)-57a: R 2 = H
(P)-(-)-57b: R 2 = CH 3
(P)-(-)-57c: R 2 = F
Ph
Ph
OH
OH
OH
OH
(P)-(+)-57d
Ph
Ph
O
O
(P)-(+)-55a: R1 = CN
(P)-(+)-55b: R1 = OMe
(P)-(+)-55c: R1 = H
(P)-(+)-55d: R1 = F
(P)-(+)-55e: R1 = CH 3
O
O
O
O
R 1
R 1
Ph
Ph
O
O
O
O
O
O
(P)-(+)-56
Fig. 4.20 Enantioenriched tetrahydrocarbo[5]helicenic derivatives prepared by Chen et al
76
J. Crassous