Lithium hydroxide, monohydrate → HCID 53644547, compound

Participants

Reaction Steps

N-tert-butoxycarbonyl α,α-dimethylglycyl α,α-dimethylglycyl α,α-dimethylglycine methyl ester 6 (2.14 g, 5.52 mmol) was dissolved in THF (60 mL) and a solution of LiOH.H2O (0.695 g, 16.6 mmol) in de-ionized H2O (30 mL) added. The reaction mixture was stirred for 3 h at room temperature before the bulk of solvent was evaporated and the solution diluted with H2O (100 mL). The solution was washed with Et2O (2×40 mL) and acidified to pH 2 by addition of 5 M HCl. A white solid precipitated and was collected by filtration. The residue was washed with icecold H2O (30 mL) and dried under high vacuum affording the title compound as a white solid (1.84 g, 89%). The compound has been prepared before,6 but as far as we have been able to establish has not been appropriately characterised; 1H NMR (200 MHz, DMSO-d6) δ 11.84 (br s, 1H, COOH), 7.59 (s, 1H, NH(Aib)), 7.48 (s, 1H, NH(Aib)), 7.18 (s, 1H, NH(Aib1)), 1.40 (s, 9H, (CH3)3), 1.32 (s, 6H, CH3), 1.28 (s, 6H, CH3), 1.25 (s, 6H, CH3); 13C NMR (75 MHz, DMSO-d6) δ 175.5, 173.5, 173.4, 155.1, 78.7, 55.8, 55.5, 54.8, 28.1, 24.8, 24.7, 24.6; HRMS (m/z): [M+Na]+ calcd. for C17H31N3O6Na, 396.2110. found, 396.2115; Anal. Calcd. for C17H31N3O6: C, 54.68; H, 8.37; N, 11.25. Found: C, 55.0; H, 8.4; N, 11.1.

Provenance & Evidence