Experimental
To (2'S,1R,2R)-2-methyl-1-(4'-aminobutane)-1-[{(2'-
ethoxymethyl)pyrrolidinyl}carbonyl]-2,5-cyclohexane (47.9 mg, 0.2 mmol) in
water (1.6 ml) was added concentrated HCl (1.6 ml) and the mixture was heated
under reflux overnight. After cooling to room temperature, the mixture was
concentrated in vacuo and dried in a freeze-drier. The crude amino acid
salt was dissolved in CH2Cl2/DMF (14.4 ml, 2:1) and DIPEA (0.15 ml, 0.9 mmol) was added. This resultant mixture was added dropwise to a solution of
(benzotriazole-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (229.0 mg, 0.4 mmol) and DMAP (53.8 mg, 0.4 mmol) in CH2Cl2/DMF (43.2 ml, 2:1)
over 8.5 h using a syringe pump. After stirring for further 13 h, the mixture
was concentrated in vacuo. The residual oil was dissolved in CH2Cl2
(50 ml) and washed with aqueous HCl solution (0.5 M, 2×50 ml).
The combined aqueous layers were extracted with CH2Cl2 (60 ml). The
combined organic layers were washed with saturated NaHCO3 solution (60 ml),
dried over anhydrous MgSO4, filtered and concentrated in vacuo.
Purification by flash chromatography (20:80→70:30 EtOAc-hexanes)
afforded the title compound (7.8 mg, 26%) as a white solid.
Recrystallization from CH2Cl2 afforded white prisms.
M. P. 392.4–393.4 K.
HRMS (+EI) calculated for C12H21NO [M]+: 195.1623, found
195.1621.
IR (KBr plate neat) νmax 3285, 2925, 2860, 1645, 1460, 1330, 1280, 1120 cm-1.
1H NMR (400 MHz, CDCl3) δ 5.96 (1H, s, CONH), 3.34 (1
H, m, NHCHaHb), 3.08 (1 H, m, NHCHaHb), 2.15 (3 H, m,
1-CH and 5-CHaHb and 12-CHaHb), 1.74 (3H,
m, 3-CHaHb, 5-CHaHb and 10-CHaHb), 1.50 (6 H,
m, 2-CHaHb and 4-CHaHb and 10-CHaHb and
11-CH2 and 12-CHaHb), 1.32 (2 H, m, 3-CHaHb and
4-CHaHb), 1.17 (1 H, m, 2-CHaHb), 1.00 (3H, d, J
= 7.1 Hz, 13-CH3).
13C NMR (100 MHz, CDCl3) δ 181.0 (7-CO), 47.1 (6-C),
42.0 (9-NCH2), 31.5 (1-CH), 29.6 (5-CH2 and
2-CH2), 29.4 (12-CH2), 27.9 (3-CH2), 23.3
(10-CH2), 21.7 (11-CH2), 20.6 (4-CH2), 15.5
(13-CH3).
m/z (+EI, 70 eV) 195 ([M]+, 100), 180 (20), 166 (11), 140 (16%).