137 7 222 7 2 0 69 3 1 0620 00 132 3 522 3 2 0 77 4 0 40______________________________________ sup 1 btbto refers to bis tributyltin oxide general procedure for preparing 6 o butyrylcastanospermine 1s 1 u03b1 6 u03b2 7 u03b1 8 u03b2 8a u03b2 octahydro 1 6 7 8 indolizinetetrol 6 butanoate hcl two liter scale with toluene as solvent scheme i step 1 a 2 liter three neck flask equipped with a mechanical stirrer thermometer and a dean stark trap fitted with a condenser bearing a nitrogen bubbler is charged with castanospermine 20 00 g 0 106 mol bis tributyltin oxide 115 ml and toluene 600 ml the mixture is heated to reflux and water is collected in the dean stark trap after 3 33 hours the heating is stopped and the reaction mixture is cooled to 20 u00b0 c scheme i step 2 the dean stark trap is removed from the above reaction and is replaced with a claisen adapter fitted with a nitrogen bubbler and a pressure equalizing addition funnel the reaction mixture is cooled to 13 u00b0 c and butyryl chloride 20 20 g 0 190 mol is added slowly over 10 minutes maintaining the temperature between 13 u00b0 c and 8 u00b0 c the reaction mixture is then allowed to warm to room temperature scheme i step 3 the above reaction mixture is diluted with ethanol 3c 650 ml ethanol denatured with 5 isopropanol and treated with anhydrous hydrogen chloride approximately 18 00 g 0 494 mol the reaction temperature rises from 18 u00b0 c to 30 u00b0 c during the hydrogen chloride addition the reaction mixture is seeded with several crystals of 6 o butyrylcastanospermine hydrochloride to produce a slurry of a white solid the slurry is.