1: 4-chloro-2-methoxyimino-3-oxo-butyric acid With phosphorus pentachloride in dichloromethane T=-20 - 0°C; 2: C16H20N2O5S2Si in dichloromethane T=-50 - 0°C; 3: thiourea With sodium hydrogencarbonate; trifluoroacetic acid; sodium 2-ethyl hexanoate Product distribution / selectivity; more than 3 stages;