Methanethiol → Guanidine Sulfate (1:1)

Participants

Reaction Conditions

Reaction Steps

To a solution of 7-(1-aminoethyl)camptothecin (1.9 g, 5 mmol) in 10 ml of water was added S-methylisothiourea hemisulfate (0.7 g, 2.5 mmol) at room temperature. The mixture was heated at 50° C. for 5 hr under nitrogen. The gases developed during the reaction were passed through two flasks, each containing an ethanolic solution of KOH for trapping the CH3SH by-product. The mixture was then concentrated and 50 ml of acetone was added. The precipitate was filtered and recrystallized from water to give 2.60 g (98%) of guanidine sulfate. Colorless solid, M.p. 286-287° C. (decomposed). IR (KBr): 2400-2600, 1760, 1660 cm−1. 1H-NMR (DMSO-d6) δ: 0.89 (3H, t, J=7 Hz), 1.88 (2H, q, J=7 Hz), 2.55-2.95 (4H, m, CH2 and CH2-guanidine.), 5.40 (2H, S, C5—H2), 5.80 (2H, S, C17—H2), 6.50 (1H, s, 20-O), 7.33 (1H, S, C14—H), 7.60-8.21 (4H, m, arom).Ms m/z: 531 (M+). Anal. Calcd for C23H25 N5O8S (531.55): C, 51.97: H, 4.74: N, 13.18. Found: C, 51.88; H, 4.60; N, 13.32.

Provenance & Evidence