Trifluoroacetic acid → (2S,9R)-2-Amino-11-[(benzyloxycarbonyl)amino]-7-(carbobenzyloxy)-9-(tetrahydropyran-2-yloxy)-7-azaundecanoic Acid

Participants

Reaction Steps

Trifluoroacetic acid (164 mg, 1.44 mmol) was added to a solution of 17a (360 mg, 0.72 mmol) in CHCl3 (7 mL). The solution was concentrated in vacuo. The resultant oil was dissolved in CH2Cl2 (20 mL), and 3,4-dihydro-2H-pyran (69 mg, 75 μL, 0.83 mmol) was added at room temperature. The reaction progress was monitored by TLC, and six additional portions of 3,4-dihydro-2H-pyran (69 mg each) were added over the next 31 hours. The reaction mixture was stirred for an additional 16 hours and concentrated in vacuo. The oil was dissolved in water (4 mL) and methanol (8 mL), then adjusted to pH 7 with saturated NaHCO3 solution. The solution was concentrated, and the crude oil was purified by chromatography on a C-18 column (30% acetone/water, followed by 55% acetone/water) to give 18a (219 mg, 52%) as a colorless oil: 1H NMR δ 1.20-1.98 (m, 14H), 3.06-3.56 (m, 8H), 3.68-4.02 (m, 2H), 4.33-4.62 (m, 1H), 5.06 (s, 2H), 5.11 (s, 2H), 7.24-7.36 (m, 10H); 13C NMR δ 20.7, 21.1, 21.7, 23.6, 26.3, 26.5, 32.0, 32.5, 34.2, 38.1, 38.5, 52.0, 56.2, 64.2, 65.2, 67.3, 68.3, 74.9, 100.1, 101.6, 128.79, 128.96, 129.02, 129.10, 129.20, 129.47, 129.56, 129.62, 138.3, 138.5, 158.0, 158.7, 174.8; HRMS m/z calcd for C31H43N3NaO8 608.2948, found 608.2954.

Provenance & Evidence