Absolute Configurational Studies of Arylalkylamines by Circular Dichroism Measurements and Gas Chromatography

Enantiodivergent Synthesis of (R)- and (S)-Rolipram

“…A similar substituent in the 3-position, on the other hand, enhances the CD effect observed in the unsubstituted case. However, for the corresponding acetamide, 10, a different substituent effect is observed; in fact, the CE's of the 4-MeO derivative (11) and the parent molecule are very similar, but the 3-MeO analogue (12) shows a CE with the opposite sign [25]. From these data alone, one cannot confidently predict the effect of two alkoxy substitutions on the CD spectrum of the corresponding acetamides.…”

“…In both pairs of diastereoisomers 8 and 9, the presence of two differentially substituted benzylic chiral moieties may be expected to give rise to additional CE's. In this case, however, all four diastereoisomeric amides of (S)-phenylethyl amine show pronounced negative CE's in the region 190-215 nm, analogous to those found for (S)-phenylethylacetamide (10) [25,26]. The CD spectrum of 10 in methanol, presents minima at λ max (∆ε)= 197.5 (− 28.5), 211 (−13.3), and 215 (-12.8) nm, which are associated with the corresponding 1 L a absorption band.…”

Asymmetric Synthesis of Nonracemic Primary Amines via Spiroborate-Catalyzed Reduction of Pure (E)- and (Z)-O-Benzyloximes: Applications toward the Synthesis of Calcimimetic Agents

“…(S)-N-[1- ethyl] acetamide (5b). 26 The crude acetamide was purified by preparative TLC using petroleum ether/ethyl acetate (3:1) as an oil (256 mg, 88%): chiral GC [method isothermal 145 °C/flow = 0.8 mL/min, t R 20.6 (97.4), 21.1 (2.6)] 95% ee; [α] D 22 = −104 (c 0.28, CHCl 3 ); 1 H NMR (400 MHz, CDCl 3 ) δ 1.50 (d, J = 6.8 Hz, J = 7.2 Hz, 3H), 2.08 (s, 3H), 3.84 (s, 3H), 5.12 (m, J = 7.2 Hz, 1H), 6.0 (s, 1H), 6.83 (m, 1H), 6.93 (d, J = 8 Hz, 1H), 7.29 (t, J = 8 Hz, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ 21.7, 23.4, 48.8, 55.2, 112.3 112.4, 118.4, 129.7, 144.9, 159.8, 169.1; FT-IR (ν, cm −1 ) 3253, 3068, 2975, 1643, 1532, 827, 755.…”