(R)-(+)- and (S)-(–)-1-(9-Phenenantryl)ethylamine: Assignment of Absolute Configuration by CD Tweezer and VCD Methods, and Difficulties Encountered with the CD Exciton Chirality Method

In agreement with predictions from the stereochemical outcome of pyruvate hydrogenation with chiral 1-(9-phenanthryl)ethylamine (1), the (+) isomer (as measured in CHCl3) was assigned the (R) configuration by use of the Zn-porphyrin host-guest CD exciton chirality method after derivatization with 4-[(Boc-amino)methyl]pyridine-2-carboxylic acid, and also directly on the amine by use of the VCD method. Attempts to use the bis(chromophoric) CD exciton chirality method after derivatization with a naphthimido group happened to be more difficult because of the complex electronic structure of the phenanthryl group, although the naphthimido moiety was the most suitable chromophore in this case. The results are discussed.