H. Uchiro et al. / Tetrahedron Letters 54 (2013) 506–511
511
2. Hazuda, D.; Blau, C. U.; Felock, P.; Hastings, J.; Pramanik, B.; Wolfe, A.;
Bushman, F.; Farnet, C.; Goetz, M.; Williams, M.; Silverman, K.; Lingham, R.;
Singh, S. B. Antiviral Chem. Chemother. 1999, 10, 63.
3. Yang, Y. L.; Lu, C. P.; Chen, M. Y.; Chen, K. Y.; Wu, Y. C.; Wu, S. H. Chem. Eur. J.
2007, 13, 6985.
4. Suzuki, S.; Hosoe, T.; Nozawa, K.; Kawai, K.; Yagushi, T.; Udagawa, S. J. Nat. Prod.
2000, 63, 768.
5. West, R.; Van Ness, J.; Varming, A.-M.; Rassing, B.; Biggs, S.; Gasper, S.;
Mckernan, P.; Piggott, J. J. Antibiot. 1996, 49, 967.
16. Experimental procedure of one-pot four-step cascade reaction for the synthesis of
oteromycin (1a): To a solution of lactam 47 (10.0 mg, 0.0159 mmol) in THF
(1.5 mL) was added NaHCO3 (2.81 mg, 0.0333 mmol) at 0 °C. After stirring for
30 min at 0 °C, MMPP (15.7 mg, 0.0318 mmol) was added, and then the
resulting mixture was stirred at room temperature for 2 h. The reaction was
quenched with saturated aqueous Na2S2O3 solution at 0 °C, and the resulting
mixture was extracted with AcOEt. The organic layer was washed with water
and brine, dried over anhydrous sodium sulfate, filtrated, and concentrated
under reduced pressure. The residue was purified by silica gel column
chromatography (Hexane/AcOEt = 2:1) to afford the desired oteromycin (1a)
(4.0 mg, 51%) as a white amorphous with its diastereomer 1b (1.6 mg, 20%) as a
white amorphous.
6. Kontnik, R.; Clardy, J. Org. Lett. 2008, 10, 4149.
7. (a) Uchiro, H.; Shionozaki, N.; Kobayakawa, Y.; Nakagawa, H.; Makino, K. Bioorg.
Med. Chem. Lett. 2012, 22, 4765; (b) Shionozaki, N.; Yamaguchi, T.; Kitano, H.;
Tomizawa, M.; Makino, K.; Uchiro, H. Tetrahedron Lett. 2012, 53, 5167.
8. Eade, S. J.; Walter, M. W.; Byrne, C.; Odell, B.; Rodriguez, R.; Baldwin, J. E.;
Adlington, R. M.; Moses, J. E. J. Org. Chem. 2008, 73, 4830.
9. Tortosa, M.; Yakelis, N. A.; Roush, W. R. J. Org. Chem. 2008, 73, 9657.
10. N-Teoc-protected c-methoxylactam 9 was synthesized by a similar manner to
17. Physical data of synthesized oteromycin (1a): ½a D20
= ꢀ116 (c = 0.2, MeOH); lit.
ꢁ
½
a 2D2
ꢁ
= ꢀ60 (c = 0.5, MeOH) (See Ref. 1), 1H NMR (400 MHz, CD2Cl2) d 7.40 (1H,
d, J = 1.9 Hz), 7.24–7.35 (6H, m), 6.10 (1H, brs), 5.48 (1H, brs), 5.39 (1H, brs),
5.20 (1H, q, J = 6.8 Hz), 3.73 (1H, dd, J = 7.8, 12.2 Hz), 3.17 (1H, d, J = 13.6 Hz),
3.12 (1H, brd, J = 8.0 Hz), 3.04 (1H, d, J = 13.6 Hz), 1.62 (3H, brd, J = 7.1 Hz), 1.61
(3H, s), 1.49 (3H, d, J = 1.0 Hz), 1.46 (3H, s), 1.41–1.80 (5H, m), 0.91–0.98 (3H,
m), 0.90 (3H, s), 0.86 (3H, d, J = 6.1 Hz) ppm; 13C NMR (100 MHz, CD2Cl2) d
196.3, 167.7, 154.3, 137.0, 136.8, 135.8, 134.7, 134.1, 133.8, 130.8, 130.0, 128.8,
127.7, 124.7, 86.0, 51.4, 50.2, 48.8, 43.8, 40.3, 36.1, 35.4, 27.8, 24.7, 22.9, 22.0,
that of N-Boc-protected one. (See Ref. 7a).
11. Physical data of endo-type pentacyclic compound 24a: ½a D22
= ꢀ62 (c = 0.050,
ꢁ
CHCl3); 1H NMR (400 MHz, DMSO) d 7.50 (1H, s), 7.35–7.31 (2H, m), 7.21–7.16
(3H, m), 6.20 (1H, s), 5.61 (1H, s), 5.38 (1H, s), 4.02 (1H, d, J = 10.5 Hz), 3.35 (1H,
d, J = 9.5 Hz), 2.95 (1H, m), 2.64 -2.59 (1H, dd, J = 12.5, 11.0 Hz), 2.57 (1H, m),
1.80 (3H, s), 1.72 (3H, s), 1.65–1.61 (1H, m), 1.54 (3H, s), 1.51–1.46 (1H, m),
1.37–1.30 (1H, m), 1.14 (3H, d, J = 7.6 Hz), 0.98 (3H, s), 0.83 (3H, d, J = 5.1 Hz),
0.83–0.93 (4H, m) ppm; 13C NMR (100 MHz, DMSO) d = 212.2, 173.3, 138.4,
138.0, 136.8, 136.4, 132.6, 131.0, 129.2, 127.7, 126.6, 105.3, 48.5, 47.0, 44.2,
44.1, 43.9, 43.9 36.0, 35.9, 33.1, 30.0, 27.7, 25.8, 23.4, 22.9, 21.3, 20.3, 16.9,
20.6, 16.6, 15.1, 13.6 ppm; IR (ATR)
1451, 1377, 1212, 1086, 1038, 955, 858, 702 cmꢀ1; HRMS (FAB) calcd for
32H42NO3: 488.3165; found: 488.3160 [M+H]+.
18. Physical data of exo-type pentacyclic compound 48:
mmax = 3310, 2949, 2912, 1723, 1606, 1497,
C
½ ꢁ = ꢀ133 (c = 0.060,
a 2D3
CHCl3); 1H NMR (400 MHz, DMSO) d 8.67 (1H, s), 7.32–7.23 (5H, m), 5.74 (1H,
s), 5.33 (1H, s), 5.09 (1H, s), 2.99 (2H, s), 2.73 (1H, d, J = 8.3 Hz), 2.48 (1H, s),
2.09–1.99 (2H, m), 1.83 (3H, s), 1.58 (3H, s), 1.48 (3H, s), 1.64–1.23 (3H, m),
0.99 (1H, q, J = 12.9 Hz), 0.90–0.77 (2H, m), 0.75 (3H, d, J = 7.8 Hz), 0.74 (3H, s),
0.72 (3H, d, J = 7.3 Hz), 0.58 (1H, t, J = 12.2 Hz), 0.46 (1H, dq, J = 12.4, 3.4 Hz)
ppm; 13C NMR (100 MHz, DMSO) d = 218.7, 174.6, 137.9, 136.4, 134.6, 130.6,
128.0, 127.9, 126.5, 126.0, 87.7, 63.5, 50.0, 49.4, 48.6, 47.7, 44.9, 43.6, 40.9,
35.5, 35.3, 28.7, 26.6, 25.4, 24.9, 22.9, 22.6, 22.3, 19.9, 19.4 ppm; IR (ATR)
16.2 ppm; IR (ATR)
HRMS (EI) calcd. for C32H39NO2 469.2981, found 469.2986.
12. Interestingly, thermal IMDA reaction of -methoxylactam 22 did not proceed
m ;
max = 2923, 2349, 2145, 1670, 1219, 1029, 822, 718 cmꢀ1
c
at higher temperature (in toluene, reflux). It is supported that the observed
IMDA reaction under the acidic condition proceeded via more reactive iminium
ion intermediate 23.
13. Snider, B. B.; Neubert, B. J. J. Org. Chem. 2004, 69, 8952.
14. Similar interesting oxidative approaches to synthesize the non-
mmax = 3284, 2947, 2920, 1733, 1683, 1496, 1455, 1376, 1227, 1119, 859,
a-acyl-type
702 cmꢀ1; HRMS (ESI) calcd for C32H42NO3 [M+H]+ 488.3159, found 488.3158.
19. Pornpakakul, S.; Roengsumran, S.; Deechangvipart, S.; Petsom, A.; Muangsin,
N.; Ngamrojnavanich, N.; Sriubolmas, N.; Chaichit, N.; Ohta, T. Tetrahedron Lett.
2007, 48, 651.
c
-hydroxy- -lactams (5-hydroxypyrrol-2(5H)-ones) were reported by two
c
groups: (a) Boukouvalas, J.; Xiao, Y.; Cheng, Y. X.; Loach, R. P. Synlett 2007,
20, 3198; (b) Kiren, S.; Hong, X.; Leverett, C. A.; Padwa, A. Tetrahedron 2009,
65, 6720; (c) Boukouvalas, J.; Loach, R. P.; Ouellet, E. Tetrahedron Lett. 2011,
52, 5047.
15. In this reaction, the chiral lactam 43 was used because the yield of the aldol
reaction with decalin aldehyde 8 (94%) was superior to that of using its
enantiomer 38 (47%).