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T. Nishii et al. / Tetrahedron Letters 44 (2003) 7829–7832
11. (R)-2-Methylbutanoic acid was prepared following the
procedure in the literature. See, (a) Spino, C.; Beaulieu,
C. J. Am. Chem. Soc. 1998, 120, 11832–11833; (b) Spino,
C.; Beaulieu, C.; Lafreniere, J. J. Org. Chem. 2000, 65,
7091–7097.
1604, 1537 cm−1; MS (FAB) m/z 521 (M++1), 419, 329,
278, 236, 91 (bp); HRMS m/z 521.2463 (521.2499 calcd
for C26H37O9N2).
(+)-AA3a(R): colorless needles (rotamer mixture): mp
156.5ꢀ157.0°C (ether/pet. ether); [h]2D0 +74.4 (c 0.36,
1
CHCl3): H NMR (600 MHz, CDCl3) l 12.63 and 12.47
12. The physical properties were as follows:
(total integr. 1H, s and s), 8.79 and 8.51 (total integr. 1H,
d, J=12 Hz and d, J=1.8 Hz), 8.56 and 7.38 (total
integr. 1H, dd, J=7.8, 1.2 Hz and br.d, J=7.8 Hz), 7.95
and 7.76 (total integr. 1H, br.s and br.d, J=11.4 Hz),
7.29 and 7.25 (total integr. 1H, br.d, J=7.2 Hz and dd,
J=7.8, 1.2 Hz), 7.08 and 7.06 (total integr. 1H, br.d,
J=7.2 Hz and br.d, J=7.2 Hz), 6.93 and 6.90 (total
integr. 1H, t, J=7.8 Hz and t, J=7.8 Hz), 5.74 (1H, dq,
J=7.8, 6.6 Hz), 5.30 and 5.29 (total integr. 1H, t, J=7.8
Hz and t, J=7.8 Hz), 5.10 and 5.09 (total integr. 1H, t,
J=9.6 Hz and t, J=10.2 Hz), 5.00 (1H, dq, J=9.6, 6.6
Hz), 2.54 (1H, ddd, J=12.0, 10.8, 3.0 Hz), 2.43 (1H, ddq,
J=7.8, 7.2, 7.2 Hz), 1.75ꢀ1.67 (1H, m), 1.74 (1H, ddq,
J=15.0, 7.8, 7.8 Hz), 1.49 (1H, ddq, 15.0, 7.2, 7.8 Hz),
1.39ꢀ1.23 (4H, m), 1.32 (3H, d, J=6.6 Hz), 1.30 (3H, d,
J=6.6 Hz), 1.21ꢀ1.11 (1H, m), 1.20 (3H, d, J=7.2 Hz),
0.94 (3H, dd, J=7.8, 7.2 Hz), 0.87 (3H, t, J=7.2 Hz); IR
(neat) 3370, 2963, 2935, 2875, 1747, 1688, 1643, 1610,
1534 cm−1; MS (FAB) m/z 521 (M++1), 265, 237, 164,
136 (bp); HRMS m/z 521.2527 (521.2499 calcd for
C26H37O9N2).
(+)AA3a(S): colorless needles (rotamer mixture): mp
173.1ꢀ174.0°C (ether/pet. ether); [h]2D1 +91.6 (c 0.32,
1
CHCl3): H NMR (600 MHz, CDCl3) l 12.63 and 12.47
(total integr. 1H, s and s), 8.79 and 8.51 (total integr. 1H,
d, J=11.4 Hz and d, J=1.2 Hz), 8.55 and 7.38 (total
integr. 1H, dd, J=7.8, 1.2 Hz and br.d, J=7.2 Hz), 7.98
and 7.78 (total integr. 1H, br.s and br.d, J=11.4 Hz),
7.30 and 7.25 (total integr. 1H, br.d, J=7.2 Hz and dd,
J=7.8, 1.2 Hz), 7.09 and 7.07 (total integr. 1H, br.d,
J=7.2 Hz and br.d, J=7.2 Hz), 6.92 and 6.90 (total
integr. 1H, t, J=7.8 Hz and t, J=7.8 Hz), 5.75 (1H, dq,
J=7.8, 6.6 Hz), 5.31 and 5.29 (total integr. 1H, t, J=7.8
Hz and t, J=7.2 Hz), 5.11 and 5.09 (total integr. 1H, t,
J=10.2 Hz and t, J=10.2 Hz), 5.00 (1H, dq, J=9.6, 6.6
Hz), 2.53 (1H, ddd, J=12, 10.2, 3.6 Hz), 2.43 (1H, ddq,
J=7.8, 7.2, 6.6 Hz), 1.75ꢀ1.67 (1H, m), 1.74 (1H, ddq,
J=14.4, 7.2, 7.8 Hz), 1.50 (1H, ddq, J=14.4, 7.8, 7.2
Hz), 1.39ꢀ1.23 (4H, m), 1.32 (3H, d, J=6.6 Hz), 1.29
(3H, d, J=6.6 Hz), 1.21ꢀ1.11 (1H, m), 1.19 (3H, d,
J=6.6 Hz), 0.95 (3H, dd, J=7.8, 7.2 Hz), 0.87 (3H, t,
J=7.2 Hz); IR (neat) 3370, 2963, 2875, 1747, 1684, 1644,