Diastereoselective Hydroborations Diastereoselective Hydroborations a Erythronolide synthesis: Annette Kim 3 ThexylBH2 ETHF,0° C-art TBSO Et TBsO 797800 9BBN85:1570% BH3THF 05 84% mixture of the lactol lactone I ized to the keto-lactone in a Lonomycin synthesis: Andy Ratz 60%) BH3THF unexpectedly provided the anti isomer in high selectivity 9-BBN Diastereoselection>95: 5(antij r I Anti-selective hydroborations with borane (85%) Diastereoselection 92: 8(syn) I The sense of asymmetric induction is completely turned over in Andy 's reaction when using R2BHeBH3 K Mon Diastereoselection 92: 8(anti) Tetrahedron 1979. 32. 1979 Bull. Chem. Soc. Jpn., 1992, 65, 2974 REH reselection 6.8: 1(anti BH3. DMS 17: 83 Oikawa& Co-workers Tetrahedron Lett, 1983, 19, 1987 reselection 6.6: 1 (anti) 10A-09-Hydroboration-2 10/8/00 8: 13 PMI. Paterson & J. Channon Tetrahedron Lett., 1992, 33, 797-800. BH3•THF unexpectedly provided the anti isomer in high selectivity 5 anti syn 74% 89% yield 95 : 05 >95 : 05 9-BBN BH3•THF anti : syn anti : syn 9-BBN BH3•THF 85 : 15 05 : 95 yield 70% 84% anti syn 80% 99% yield 82 : 18 17 : 83 (Chx)2BH BH3•DMS anti : syn anti syn The sense of asymmetric induction is completely turned over in Andy's reaction when using R2BH↔BH3 ■ Erythronolide synthesis: Annette Kim Diastereoselection 93 : 7 THF, 0 °C→rt 12 h 3 ThexylBH2 ■ Lonomycin synthesis: Andy Ratz Diastereoselective Hydroborations BH3•DMS (85%) Diastereoselection > 95 : 5 (anti) 9-BBN (60%) Diastereoselection 92 : 8 (syn) Nakata, Tatsuta & Co-workers, Bull. Chem. Soc. Jpn., 1992, 65, 2974. Diastereoselective Hydroborations BH3•THF BH3•THF Diastereoselection 92 : 8 (anti) R = H Diastereoselection 6.8 : 1 (anti) R = OBn Diastereoselection 6.6 : 1 (anti) K. Mori Tetrahedron 1979, 32, 1979. Oikawa & Co-workers Tetrahedron Lett., 1983, 19, 1987. ■ Anti–selective hydroborations with borane A 2:1 mixture of the lactol:lactone was obtained. This mixture was oxidized to the keto-lactone in 73% overall yield from the olefin. Me OH Me H O Me Me OMe Me OMe Me XP O OH OH OH OBn OH Me OBn OH Me O Me OH XP Me OMe Me OMe Me O H Me OH Me Me OH Me H O Me OMe Me OMe Me XP O O Et OH Me O Me TBSO Me Me TBSO Me Me Et O OH O OH Et Me O Me TBSO Me OH OH Me OBn OH Me OH OH Me OH Me OBn OBn OH OBn Me Me OH Me OBn OBn OBn OH Me OH OH OH OH OH OH Me OH OBn OBn Me OBn OH Me Me OBn OH OBn Me OBn OH Me OH Me O O O O Me Me Me Me O BnO R Me Me O O Me R BnO OH Me O Me O O OH 10A-09-Hydroboration-2 10/8/00 8:13 PM