Total Synthesis of xazolomycin A Me xazolomycin A Me Eto, K.; Yoshino, M.; Takahashi K.; Ishihara, J.; atakeyama S. rg. Lett. 2011, 13, 5398 Dimas Paz Wipf group- Current Literature ctober 8, 2011 Dimas Paz @ Wipf Group Page 1 of 14 12/28/2011
xazolomycin A - Isolation and Biological Active xazolomycin A was isolated from a strain Streptomyces together with eooxazolomycin in 1985 by Uemura at al. xazole polyene lactam-lactone xazolomycin A Me Me eooxazolomycin Me They exhibit wide ranging and potent antibacterial and activities as well as in vivo antitumor activity. a) Mori, T.; Takahashi, K.; Kashiwabara, M.; Uemura, D.; Katayama, C.; Iwadare, S.; Shizuri, Y.; Mitomo, R.; akano, F.; Matsuzaki, A. Tetrahedron Lett. 1985, 26, 1073. b) Takahashi, K.; Kawabata, M.; Uemura, D.; Iwadare, S.; Mitomo,R.; akano, F.; Matsuzaki, A. Tetrahedron Lett. 1985, 26, 1077. Moloney, M. G.; Trippier, P. C.; Yaqoob, M.; Wang, Z. Curr. Drug. Discovery Technol. 2004, 1, 181 Dimas Paz @ Wipf Group Page 2 of 14 12/28/2011
Retrosynthesis Bn Me C 2 Me C 2 Me Me xazolomycin A Me Bn Conia-ene type cyclization C 2 Me C 2 Me Me Amidation Me Dihydroxylation ozaki-iyama-kishi Me Bn C 2 Me Me Fmoc I P Me P P Me Dimas Paz @ Wipf Group Page 3 of 14 12/28/2011
Synthesis of the γ-lactone Bn Me TBDPS + Bn Tf 1. n-buli, DMPU/TF!78 C 2. TBAF, TF 81% (2 steps) Bn 1. 2 Cr 4, aq acetone, 0 C 2. SCl 2, C 2 Cl 2 3. toluene C 2 Me Me C 2 Me 63% (3 steps) Bn Me C 2 Me C 2 Me In(Tf) 3 (5 mol%) DBU (4.4 mol%) toluene, reflux 91% Bn C 2 Me C 2 Me Me nyango, E..; Tsurumoto, J.; Imai,.; Takahashi, K.; Ishihara, J.; atakeyama, S. Angew. Chem. Int. Ed. 2007, 46, 6703. Dimas Paz @ Wipf Group Page 4 of 14 12/28/2011
Plausible mechanism - In(III)-catalyzed Conie-ene type cyclization Endo, K.; atakeyama, T; akamura, M.; akamura, E. J. Am. Chem. Soc. 2007, 129, 5264 Dimas Paz @ Wipf Group Page 5 of 14 12/28/2011
Bn Synthesis of the γ-lactone C 2 Me C 2 Me s 4, M Me TF- 2 Bn 100% C 2 Me Me Bn Me 1. Li, TF then Cl (1 M) 2. (CCl) 2, DMF (cat.), C 2 Cl 2 then ab 4, TF-Me!78 C, 60% Bn Me 17 was supported by ESY spectrum in [D 8 ]TF/D 2 and also suggested to be energetically most stable by Molecular mechanics calculation. Dimas Paz @ Wipf Group Page 6 of 14 12/28/2011
Synthesis of the right-hand segment P Me P P Me Bn 1. MMCl, i-pr 2 Et, C 2 Cl 2 Me 2. ab 4, TF-Et 3. TBSTf, 2,6-lutidine C 2 Cl 2,!78 C 93% (3 steps) Bn TBS MM Me Me 3 + BF 4 - proton sponge 4 Å MS, C 2 Cl 2 95% Me Bn ZrCl 4, i-pr reflux TBS MM Me Me Bn 1. TBAF, TF 2. 2 Cr 4, acetone, 0 C Me 3. acl 2, a 2 P 4 2-methyl-2-butene t-bu- 2 n-c 12 25 SC 2 TIPS CuBr 2, n-bu 4 Br Bn Me Et 3, 4 Å MS, C 2 Cl 2 67% (5 steps) Bn Me MM Me TIPS Me Dimas Paz @ Wipf Group Page 7 of 14 12/28/2011
Synthesis of the right-hand segment Bn Me TIPS Me i-pr 2 Si(Tf) 2, 2,6-lutidine ClC 2 C 2 Cl, reflux, 90% Bn Me Si TIPS Me P Me P P Me TIPS 1. 2, Pd() 2, AcEt 2. Dess-Martin periodinane ac 3, C 2 Cl 2 92% (2 steps) Me Si Me Synthesis of the middle segment Fmoc I 2 FmocCl ac 3 dioxane 96% Fmoc acrolein oveyda-grubbs 2nd C 2 Cl 2, 85% Fmoc C CrCl 2, CI 3 TF Fmoc I 68% (E:Z = 8:1) Dimas Paz @ Wipf Group Page 8 of 14 12/28/2011
Synthesis of the left-hand segment Me Ac EtCCl, LiCl 4, i-pr 2 Et C 2 Cl 2 -Et 2, -78 C, 92% 98% ee, >99% de Plausible mechanism C R 3 * R 1 R 3 * + M R 1 Lewis acid M (M) R 3 * R 1 R 2 C R 3 * = Me M R 1 R 2 M R 1 R 2 R 1 R 2 R 3 * R 3 * Zhu, C.; Shen, X.; elson, S. C. J. Am. Chem. Soc. 2004, 126, 5352 Dimas Paz @ Wipf Group Page 9 of 14 12/28/2011
Synthesis of the left-hand segment Ac ame Me, 95% C 2 Me LDA, MeI TF,!20 C 84% C 2 Me 1. ame, Me 2. TBSTf 2,6-lutidine, C 2 Cl 2 0 C, 98% (2 steps) TBS C 2 Me 1. n-buli, I 2, TF,!78 C 2. o-( 2 )C 6 4 S 2 2 Et 3, i-pr-tf 92% (2 steps) I TBS C 2 Me Pd(PPh 3 ) 4, CuI CsF, DMF 1. F, MeC 2. Li, TF- Me 83% SnBu 3 TBS Me 3. Ac 2, pyridine ac 3, Me 88% Ac Dimas Paz @ Wipf Group Page 10 of 14 12/28/2011
Synthesis of the left-hand segment Ac Et Et 1. KSC, Cl, MeC, reflux 2. K, n-bui, TF 79% (2 steps) BuS t-buli, CuC 2 LiCl TF,!78 C BrC 2 CCSiMe 3!78 C - rt, 94% BuS 1. Raney i, acetone: Et reflux, 92% 2. AgTf, C 2 Cl 2 /Me/ 2, 73% n-bu 3 Sn, AIB 70 C, 88% SnBu 3 E/Z = 6:1 Dimas Paz @ Wipf Group Page 11 of 14 12/28/2011
Synthesis of xazolomycin A TIPS Ac Me Me Me Si Me Fmoc I Dimas Paz @ Wipf Group Page 12 of 14 12/28/2011
Synthesis of xazolomycin A TIPS Me Si Me 1. icl, CrCl 2, TF-DMS Fmoc 2. Dess-Martin periodinane ac 3, C 2 Cl 2 3. L-selectride, TF,!78 C 53% (3 steps) I Fmoc Me TIPS 7R + 7S-epimer Pr Me Si Pr 4:1 1. Ac 2, pyridine, 91% 2. DBU, C 2 Cl 2 then BPCl, Et 3, C 2 Cl 2 68% (2 steps) Ac Ac Me Si TIPS Me 1. F pyridine, TF 2. Li, TF Ac ATU, i-pr 2 Et, TF 41% (3 steps) Me Me xazolomycin A Me Me Dimas Paz @ Wipf Group Page 13 of 14 12/28/2011
Summary and utlook Me xazolomycin A Me xazolomycin A was synthesized in 34 steps of the longest linear sequence in 1.4% overall yield from methyl (S)-3-hydroxy-2-methylproprionate. Key transformation include In(III)-catalyzed Conia-ene type cyclization, Cinchona alkaloid-catalyzed cyclocondensation and asymmetric dihydroxylation. Dimas Paz @ Wipf Group Page 14 of 14 12/28/2011