of identical quality crystals 58 2 g gt 99 d e were obtained from the liquors overall yield 41 1 h nmr 400 mhz d 6 dmso 7 37 5h m 5 08 2h m 4 64 2h m 3 90 1h br s 3 70 1h dt j 8 5 3 5 3 59 3h br s 3 47 u2013 3 27 1h br m 2 19 1h m 1 82 1h dd j 13 5 6 5 1 54 2h m gc material derived to acetate gave retention times 28 2 minor diastereoisomer 29 0 major diastereoisomer in a ratio 1 220 synthesis of n benzyloxycarbamoyl 2r carbomethoxy 4s hydroxypiperidine was carried using the same method and resulted in an equivalent product an x ray structure was used to confirm the stereochemistry of this compound n benzyloxycarbamoyl 2s carbomethoxy 4s hydroxypiperidine 4 hemiphthalate 365 g 0 82 mol was mixed with 2m hcl 1 5 l and heated to reflux for 5 days the mixture was cooled and extracted with etoac 3 u00d7 1 l the aqueous layer was concentrated in vacuo to leave a cloudy paste 170 g this was redissolved in h 2 o 500 ml and the solution neutralised using amberlite ira 93 the resin was filtered and washed with h 2 o 1 5 l the filtrate was concentrated in vacuo and dried by azeotroping with.