1. Enantioselective Total Synthesis and Structure Revision of Spirodihydrobenzofuranlactam 1. Total Synthesis of Stachybotrylactam Org. Lett. 2003, 5, 1785 이화여대 분자생명과학부 화학전공 022LBG19 이지윤

2. Introductions A series of spirodihydrobenzofuranlactams were isolated from the cultures of two different Stachybotrys species by Roggo et al. in 1996. They have an activity as antagonists of endothelin and as inhibitors of HIV-1 protease. These novel spirodihydrobenzofuranlactams were reported to contain the unique axial hydroxyl group at the C-19 position and the benzofuranlactam moiety. The pseudosymmetric dimer 5 is the most potent representative of this series. Kende ’ s group tried enantioselective total synthesis of structure 1 and its regioisomer 25 as well as their comparisons with natural material due to their undetermined absolute configuration and pharmacological activity. 1

3. Retrosynthetic Analysis 2

4. Scheme 1. Synthesis of trans-Decalone 6 3

5. Mechanisms 4

6. 5

7. 6

8. 7

9. Scheme 2. Construction of AB-Ring Segment 10 8

10. 9 Mechanisms

11. 10

12. 11

13. Scheme 3. Attemped Spiroannulation of C- and D-Rings 12

14. 13 Mechanisms

15. 14

16. 15

17. Scheme 3. Attemped Spiroannulation of C- and D-Rings 16

18. 17 X-ray structure of cpd 15

19. 18 Mechanism

20. Scheme 4. Construction of E-Ring Spirodihydrobenzofuranlactam The structure of cpd 1 was confirmed by single-crystal X-ray analysis 19

21. 20 Mechanisms

22. 21

23. Scheme 5. Synthesis of Regioisomer 25 isolated in 1995 by Jarvis et al. [α] 20 D =-21.3 (c 1.10, MeOH) Stachybotrylactam 22

24. Conclusions A series of spirodihydrobenzofuranlactams were isolated from the cultures of two different Stachybotrys species by Roggo group in 1996. The enantioselective total synthesis of spirodihydrobenzofuranlactam 1 was achieved via 20 steps in 5.1% overall yield from the optically pure (+)-Wieland- Miescher ketone. And its regioisomer 25 stachybotrylactam was also synthesized. The structures of compound 1, 10, 13, 15, 17, 20, 21, and 23-25 were confirmed by 1 H and 13 C NMR spectra. The 1 H and 13 C NMR spectra of the synthetic compound 1 were not identical to those reported for the natural spirodihydrobenzofuranlactam 1 revealed by Roggo. Comparisons of 1 H and 13 C NMR spectra of the synthetic 25 with the natural spirolactam isolated by Roggo et al. and with stachybotrylactam isolated by Jarvis reported to have structure 1. The absolute configuration of the natural lactam could not be established because neither the Roggo group nor the Jarvis laboratories has reported its optical rotation. A very closely related spirobenzofuranlactam N-ethanol derivative reported by Jarvis has the negative sign of optical rotation ([α] 20 D = -16, c 0.1, MeOH), which is very similar to that of the synthetic lactam 25 ([α] 20 D = -21.3, c 1.10, MeOH). Thus, the absolute configuration of natural stachybotrylactam is most likely represented by stereoformula 25. 23