d j 6 6 hz isomer 74 7 29 4h m arh 7 22 1h m arh 5 11 1h dd j 5 6 9 4 hz 4 29 1h br nhboc 3 81 1h dd j 4 6 9 8 hz 3 65 3h s och 3 3 59 1h dd j 10 8 15 2 hz 3 19 1h dd j 5 5 15 2 hz 3 13 1h dd j 4 5 13 8 hz 2 94 2h m 39 s 2 71 1h m 2 64 1h dd j 10 3 13 3 hz 2 17 h 2 o 1 76 1h m 1 69 2h m 1 57 2h m 1 36 9h s boc 0 93 6h d j 6 5 hz 13 c nmr 75 mhz cdcl 3 8 isomer 75 5s 175 2 172 5 155 9 138 9 129 3 128 5 126 4 79 2 60 91 60 62 55 65 52 19 45 70 43 98 38 12 37 99 33 46 28 30 boc 25 01 23 10 21 93 isomer 74 5r 175 1 172 5 155 7 139 3 129 3 128 7 126 8 78 9 56 01 55 80 53 05 52 14 42 07 40 70 38 01 37 98 31 51 28 26 boc 25 03 23 11 21 74 mass spectrum isms m z 462 3 mh calculated for c 32 h 45 n 3 o 5 461 fragments or 70 406 2 tbu selective synthesis of the 3 s 5 s diastereomer 75 by the short method the 3 s 5 s diastereomer the minor product formed as described above can be.