A solution of 3.64 g (61.69 mmol) of guanidine in 150 ml of tert-butanol was added to a solution of 20 g (41.23 mmol) of (1.1) in THF and the mixture was stirred at room temperature for 18 h. A further 4.5 g of guanidine in 150 ml of tert-butanol were then added, and the reaction solution was stirred at room temperature for 7 h, concentrated to about a half and stirred at room temperature for a further 18 h. The solvent was removed in vacuo and the residue was first filtered through basic Al2O3 using CH2Cl2/MeOH/H2O (95/5/0.5) and then chromatographed on silica gel by means of MPLC using CH2Cl2/MeOH/acetic acid (90/10/0.5). 8.6 g (42%) of (1.2) were obtained.
