1: 2,2-Dimethyl-[1,3]dioxane-4,6-dione; phenol in toluene 5 h; Reflux; 2: 3,4-dihydroxy-benzaldehyde With piperidine; pyridine in toluene T=20°C; 12 h;

1: sodium hydroxide / 1 h / 0 °C 2: thionyl chloride; N,N-dimethyl-formamide / 4 h / |Reflux 3: organic base / dichloromethane / 12 h / 20 °C 4: 1-methylguanidine hydrochloride; triethylamine / dichloromethane; methanol / 20 °C / |Inert atmosphere View Scheme

1: thionyl chloride; N,N-dimethyl-formamide / 4 h / |Reflux 2: organic base / dichloromethane / 12 h / 20 °C 3: 1-methylguanidine hydrochloride; triethylamine / dichloromethane; methanol / 20 °C / |Inert atmosphere View Scheme

1: organic base / dichloromethane / 12 h / 20 °C 2: 1-methylguanidine hydrochloride; triethylamine / dichloromethane; methanol / 20 °C / |Inert atmosphere View Scheme