1: (+)-castanospermine With bis(tri-n-butyltin)oxide in toluene 3.33 h; Heating / reflux; 2: butyryl chloride in toluene T=-13 - -8°C; 0.166667 h; 3: With hydrogenchloride in ethanol; isopropyl alcohol; toluene T=18 - 30°C;