References and notes
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- Benfaremo , N. , Steenbock , M. , Klapper , M. , Müllen , L , Enkelmann , V. and Cabrera , K. 1996 . Liebigs Ann. , : 1413 – 1415 . For recent examples, see
- Einhorn , J. , Einhorn , C. , Ratajczak , F. , Gautier-Luneau , I. and Pierre , J. L. 1997 . J. Org. Chem. , 62 : 9385 – 9388 .
- Einhorn , J. , Einhorn , C. , Ratajczak , F. , Durif , A. , Averbuch , M. T. and Pierre , J. L. 1998 . Tetrahedron Lett. , 39 : 2565 – 2568 .
- Rychnovsky , S. D. , Beauchamp , T. , Vaidyanathan , R. and Kwan , T. 1998 . J. Org. Chem. , 63 : 6363 – 6374 .
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- Relative configurations of the diastereomers have been determined by 1H NMR observing the signals of their benzylic protons: they appear as a singlet in the case of the meso compound, as they are enantiotopic. In the case of the (±) compound they appear as an AB quartet, being diastereotopic.
- Substantial amounts of 2b remained at the end of the reaction if the metallation step was performed at lower temperatures or for a shorter period
- The enantiomeric purity of amine 4 has been estimated by 1H NMR at 250 MHz, adding 1 eq of (R)-(+)-α-methoxy-α-(trifluoromethyl) phenylacetic acid (Mosher's acid) to a diluted solution of 4 in CDCl3. Effective splitting of the methyl esters singlet at 3.73 ppm was observed with racemic 4.
- Direct determinations of enantiomeric purity of nitroxide 5 have failed so far. It was thus reduced back to amine 4 (Zn, HCl aq).1c Recovered 4 had an unchanged enantiomeric purity.
- De Nicola , A. , Einhorn , J. and Luche , J. L. 1991 . J. Chem. Res. (S) , : 278 We have routinely used LDA solutions prepared from diisopropylamine, isoprene and metallic lithium in THF under ultrasonic irradiation, standardized immediately before use, see