反应详情

The title compound was synthesized according to General Method I utilizing HCl (2.0 M in Et2O, 31.4 mL, 62.8 mmol) and a solution of (RS)—N-((S)-cyclopentyl(pyridin-2-yl)methyl)-2-methylpropane-2-sulfinamide (8.8 g, 31.4 mmol) in MeOH (100 mL). After the addition was complete the cooling bath was removed and the mixture was stirred at rt for 1 h. The reaction mixture was concentrated under reduced pressure and the residue was suspended in Et2O (125 mL). The precipitation was filtered off and washed with Et2O (2×125 mL) and dried under reduced pressure yielding the crude product (7.7 g, 95.0% ee (S)) as a white solid. The crude product was recrystallised from t-BuOMe (150 mL), EtOH (200 mL) and MeOH (170 mL) at 80° C. The crystals formed after the solution cooled down were collected by filtration (3.3 g, 99.0% ee (S)) and the filtrate was concentrated under reduced pressure and was recrystallised again from t-BuOMe (100 mL) and MeOH (150 mL). The second crop of crystals were collected by filtration (1.3 g, 98.0% ee (S)) resulting in a combined yield of 4.6 g, 69% isolated yield). 1H NMR (400 MHz, D2O+NaOH) δ ppm 8.81 (d, J=5.5 Hz, 1H), 8.55 (t, J=8.0 Hz, 1H), 8.06 (d, J=8.0 Hz, 1H), 7.99 (t, J=6.5 Hz, 1H), 4.53 (d, J=10.5 Hz, 1H), 2.63-2.50 (m, 1H), 2.11-2.01 (m, 1H), 1.84-1.40 (m, 6H), 1.24-1.12 (m, 1H). The ee of the compound was determined by acetylating small samples with AcCl (see example below for the synthesis) and analysing the products, (S)— and (R)—N-(Cyclopentyl(pyridin-2-yl)methyl)acetamides, by chiral HPLC: Daicel Chiralpak AD-H, 80:20 v/v heptane-EtOH (+0.2% Et3N), 1.0 mL/min, λ=230 nm, Rt=9.5 min (R), Rt=25.4 min (S).

1. additionAfter the addition
2. customwas removed
3. concentrationThe reaction mixture was concentrated under reduced pressure
4. customThe precipitation
5. filtrationwas filtered off
6. washwashed with Et2O (2×125 mL)
7. customdried under reduced pressure