Massachusetts Institute of Technology Organic Chemistry 5.512

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1 Massachusetts Institute of Technology rganic Chemistry Problem Set 6 Solutions Stereocontrolled Carbonyl Reduction and Aldol Reactions May 5, 2006 Lucy Kohnen ( The target compound was used as an intermediate in the synthesis of (-)-stemoamide by Williams in Tetrahedron Lett. 1994, 35, t-buph 2 Si, 2) B 4 3) Ts, pyridine t-buph 2 Si ac, DMS ; 3 + t-buph 2 Si C 2 3) KMn 4, a 2 P 4 t-bu t-buc, Et 3 ; t-buph 2 Si n-bu 2 BTf, Et 3 ; (C 2 ) 3 C SiPh 2 t-bu R 2 F, C; aq K 2 C 3 t-bu 2 SiTf collidine t-bu 2 Si (2) The target compound was used as an intermediate in the synthesis of the macrolide antibiotic cytovaricin by Evans in J. Am. Chem. Soc. 1990, 112, Bu 2 BTf, Et 3 ; C 2) 3 Al () 2 eq Et 2 B; ab 4 t-bu 2 SiTf Si

2 (3) The target compound was used as an intermediate in the synthesis of bleomycin by Boger in Angew. Chem. Int. Ed. 1999, 38, 449. C 2 t-bu a 3 P 3 DMF C 2 t-bu C t-bu 2 C 3 R 2 Bu 2 BTf, Et 3 a 2) 2, Pd/C t-bu 2 C t-bu 2 C 2 (4) The target compound was used as an intermediate in the synthesis of polyether antibiotic lonomycin A by Evans in J. Am. Chem. Soc. 1995, 117, Et 3 Bu 2 BTf, Et 3 ; C 3 Al () 2) t-bu 2 Si TBS DIBAL 2) Si 2 t-bu heat 2 Si 2 t-bu 2 Al(Et 3 ) 2) 2 C Si 2 t-bu TBAF 2) DIAD, Ph 3 P 3) C(Et) 3 propionic acid, heat 4) K,, 2 (5) The target compound was used as an intermediate in the synthesis of (-)-talaromycin A by Evans in J. Am. Chem. Soc. 1995, 117, EtMg; C 2) PCC (R)-Alpine-Borane

3 Al 4 C(Et) 3 pts,heat Et 2 C Al 4 2) PPh 3 C 4 (6) The target compound was used as an intermediate in the synthesis of bleomycin by Boger in Angew. Chem. Int. Ed. 1999, 38, 449. Ph 2 2 eq LDA ; I 2) 3 Al () 2 Boc 2, Et 3 t-bu t-bu t-bu Bu 2 BTf, DIEA (7) The target compound was used as an intermediate in the synthesis of leucasandrolide A by Rychnovsky in J. Am. Chem. Soc. 2001, 123, a; n-bu; C 2 (R)-Ru[BIAP] 2 2, Et t-bu 2 Si Et Et 2) t-bu 2 Si Et DIBAL- 2) Ph 3 P, I 2, Im Si 2 t-bu Ph I 2.0 eq LDA, 2) 2 S 4 (8) The target compound was used as an intermediate in the synthesis of polycavernoside A by White in J. Am. Chem. Soc. 2001, 123, C t-bu 2 Si TBS C B(Ipc) 2 (+) 2) t-bu 2 Si 2,6 lutidine TBS TBS 3 ; Ph 3 P

4 TBS TBS C Bu 2 BTf, Et 3 TBS TBS () 3 Al TBS TBS 3 SiTf TBS TBS Si 3 C (CF 3 C 2 ) 2 P KMDS 18-crown-6 t-bu 2 Si t-bu 2 Si Si 3 (9) The target compound was used as an intermediate in the synthesis of hexadepsipeptide GE3 by amada in Synlett 2002, 4, 613. Bu 2 BTf, Et 3 ; C t-bu 2 Si, 2) EtS, n-bu EtS Si 2 t-bu, Pd/C acetone C Si 2 t-bu PPh 3 C 2 Et Et 2 C Si 2 t-bu DIBAL 2) Mn 2 C Si 2 t-bu (10) The target compound was used as an intermediate in the synthesis of (+)-damavaricin D by Roush in J. Am. Chem. Soc. 1997, 119, C t-buph 2 Si, C SiPh 2 t-bu B(Ipc) 2 (+) 2), Et 3 3) 3 ; 2 S C SiEt 3 SiPh 2 t-bu Bu 2 BTf, Et 3 SiEt 3 SiPh 2 t-bu TBAF 2) 2 C() 2 pts

5 SiPh 2 t-bu 2 C SiPh 2 t-bu (1 The target compound was used as an intermediate in the synthesis of (+)-8-epi-xanthatin by Martin in rg. Lett. 2005, 7, C Ts, Et 3, DMAP C C 4, Ph 3 P n-bu; Tf KC, DMS - C Bu 2 BTf, DIEA () 2 Al 2) TBSTf TBS Mg TBS Tf Tf 2 TBS KMDS