反应详情

A solution of (S)-tert-butyl 1-fluoro-4,4-dimethyl-1-oxopentan-2-ylcarbamate (2.64 g, 10.7 mmol) in dimethylformamide (25 mL) was added under argon to a solution of (3R,3aR,6aR)-hexahydro-2H-furo[3,2-b]pyrrol-3-ol hydrochloride (assumed to be 9.73 mmol) in dimethylformamide (25 mL). The mixture was stirred for 1 hour then (S)-tert-butyl 1-fluoro-4,4-dimethyl-1-oxopentan-2-ylcarbamate (0.59 g, 2.4 mmol) was added. The mixture was stirred for 2 hours then the solvents removed in vacuo. The residue was diluted with brine (250 mL) then extracted with dichloromethane (3×100 mL). The combined organic layers were dried (Na2SO4), filtered and reduced in vacuo. Flash chromatography over silica, eluting with ethyl acetate:heptane mixtures 50:50 to 100:0 gave tert-butyl (S)-1-((3R,3aR,6R,6aS)-3-hydroxy-6-methoxydihydro-2H-furo[3,2-b]pyrrol-4(5H,6H,6aH)-yl)-4,4-dimethyl-1-oxopentan-2-ylcarbamate as a yellow solid (1.73 g, 61% calculated from amount of benzyl (R)-2-((1S,2R,5S)-3,6-dioxabicyclo[3.1.0]hexan-2-yl)-2-methoxyethyl carbamate present in the starting material). TLC (Rf=0.10, EtOAc:heptane 2:1), analytical HPLC main peak, Rt=13.445 min., HPLC-MS 331.2 [M+2H−tBu]+, 387.2 [M+H]+, 409.2 [M+Na]+, 795.4 [2M+Na]+; [□]D20+14.03° (c=1.96, CHCl3); δH (500 MHz, CDCl3) mixture of rotamers major:minor 4:3; 0.95 (9H, s, CH2C(CH3)3), 1.40 (9H, s, OC(CH 3)3), 1.38-1.55 (1.57H, m, CH2C(CH3)3), 1.58 (0.43H, dd, 9.24 Hz, CH2C(CH3)3 minor), 3.18 (0.43H, dd, J=11.56 and 9.58 Hz, NCH2CHOCH3 minor), 3.31 (0.57H, t, J=9.42 Hz, NCH2CHOCH3 major), 3.38 (0.43H, brs, OH minor), 3.45 (1.29H, s, OCH3 minor), 3.47 (1.71H, s, OCH3 major), 3.62 (0.43H, dd, 6.23 Hz, OCH2CHOH minor), 3.71-3.76 (0.43H, m, CHOCH3 minor), 3.78 (0.57H, dd, 4.23 Hz, OCH2CHOH major), 3.88-3.93 (0.53H, m, CHOCH3 major), 4.00-4.06 (1H, m, OCH2CHOH major and NCH2CHOCH3 minor), 4.11 (0.53H, dd, 7.36 Hz, NCH2CHOCH3 major), 4.24-4.34 (2.43H, m, OCH2CHOHCH and OCH2CHOH minor), 4.45-4.51 (0.43H, m, CHCH2C(CH3)3 minor), 4.67-4.73 (1.57H, m, CHCHOCH3 and CHCH2C(CH3)3 major), 5.14 (0.43H, d, J=9.35 Hz, NH minor), 5.27 (0.57H, d, J=10.03 Hz, NH major), 5.54 (0.57H, d, J=5.30 Hz, OH major); δC (125 MHz, CDCl3) 28.27/28.36 (OC(CH3)3), 29.71/29.85 (CH2C(CH3)3), 30.55/30.65 (CH2C(CH3)3), 46.14/46.96 (CH2C(CH3)3), 46.56/48.56 (NCH2CHOCH3), 48.72/49.46 (CHCH2C(CH3)3), 58.02/58.10 (OCH3), 69.96/70.33 (OCH2CHOHCH), 74.08/74.98 (OCH2CHOH), 76.37/79.71 (CHOH), 77.96/79.42 (CHOCH3), 78.44/80.45 (OCHCHOCH3), 79.82/80.45 (OC(CH3)3), 155.31/156.06 (Boc C═O), 172.64/173.24 (CH2NC═O).

1. stirringThe mixture was stirred for 2 hours
2. customthe solvents removed in vacuo
3. additionThe residue was diluted with brine (250 mL)
4. extractionthen extracted with dichloromethane (3×100 mL)
5. dry with materialThe combined organic layers were dried (Na2SO4)
6. filtrationfiltered
7. washFlash chromatography over silica, eluting with ethyl acetate