8834
G. Mehta, R. S. Kumaran / Tetrahedron Letters 46 (2005) 8831–8835
´
Cartagena, E.; Catalan, C. A. N.; Pedro, J. R. Phyto-
1H), 4.56 (s, 1H), 3.17 (qui, J = 6.9 Hz, 1H), 2.98 (dd,
J = 15.9, 11.1 Hz, 1H), 2.70–2.54 (m, 3H), 2.32–2.26 (m,
3H), 1.79 (s, 3H), 1.77 (s, 3H), 1.15 (d, J = 6.9 Hz, 3H);
13C NMR (75 MHz, CDCl3): d 211.9, 147.3, 135.9, 130.4,
127.3, 121.4, 109.6, 47.1 (2C), 40.1, 31.1, 28.0, 23.2, 22.7,
15.7; HRMS (ES): m/z calcd for C15H22ONa (M+Na):
chemistry 2001, 57, 125–130; (e) de Gutierrez, A. N.;
´
´
Bardon, A.; Catalan, C. A. N.; Gedris, T. B.; Herz, W.
Biochem. Syst. Ecol. 2001, 29, 633–647; (f) Ruzicka, L.
Bull. Soc. Chim. Belg. 1932, 41, 565.
3. For a review on the synthesis of germacrane sesquiter-
penes, see: Minnard, A. J.; Wijnberg, J. B. P. A.; de Groot,
A. Tetrahedron 1999, 55, 2115–2146.
23
241.1568; found: 241.1580. Compound (ꢀ)-38: ½aꢁD ꢀ23.2
(c 0.8, CHCl3); IR 1698 cmꢀ1 13C NMR (100 MHz,
;
4. Selected examples of syntheses of germacranes: (a) Corey,
E. J.; Hortmann, A. G. J. Am. Chem. Soc. 1965, 87, 5736–
5742; (b) Iguchi, M.; Nishiyama, A.; Yamamura, S.;
Hirata, Y. Tetrahedron Lett. 1969, 10, 4295–4298; (c)
Wharton, P. S.; Sundin, C. E.; Johnson, D. W.; Kluender,
H. C. J. Org. Chem. 1972, 37, 34–38; (d) Still, W. C. J. Am.
Chem. Soc. 1977, 99, 4186–4187; (e) Minnard, A. J.;
Wijnberg, J. B. P. A.; de Groot, A. Tetrahedron 1994, 50,
4755–4764; (f) Minnard, A. J.; Wijnberg, J. B. P. A.; de
Groot, A. J. Org. Chem. 1997, 62, 7336–7345; (g)
Nevalainen, M.; Koskinen, A. M. P. J. Org. Chem.
2002, 67, 1554–1560; (h) Smitt, O.; Hogberg, H.-E. Synlett
2002, 1273–1276; (i) Ivkovic, A.; Matovic, R.; Saicic, R.
N. Org. Lett. 2004, 6, 1221–1224.
CDCl3): d 213.5, 148.5, 136.4, 133.9, 129.3, 126.8, 110.0,
46.6, 44.3, 41.2, 40.0, 33.1, 31.3, 20.4, 17.6; HRMS (ES):
m/z calcd for C15H22ONa (M+Na): 241.1568; found:
23
241.1584. Compound (+)-40: ½aꢁD +68.2 (c 1.1, CHCl3);
IR 1702 cmꢀ1 13C NMR (75 MHz, CDCl3): d 214.5,
;
148.9, 134.1, 130.8, 129.6, 127.9, 109.2, 47.8, 47.0, 46.1,
38.8, 33.8, 21.3, 18.7, 18.5; HRMS (ES): m/z calcd for
C15H22ONa (M+Na): 241.1568; found: 241.1568.
9. Grubbs, R. H.; Chang, H. Tetrahedron 1998, 54, 4413–
4450.
10. X-ray data for 12: C14H22O2, MW = 222.32, colourless
crystal, crystal system: orthorhombic, space group:
P212121, cell parameters: a = 6.7810(40), b = 8.2778(49),
3
˚
˚
c = 22.5066(14) A, V = 1263.34(13) A , Z = 4, qcalcd
=
5. Grob-like C–C bond fragmentation6 of decalinic systems
to generate 10-membered rings and its application to the
synthesis of germacranes has been observed previ-
ously.3,4b,c,e,i Ref. 4i, reporting a RCM/fragmentation
route to a natural product periplanone C appeared while
the present work was nearing completion.
1.17 g cmꢀ3, F(000) = 487.9, l = 0.076 mmꢀ1, total no.
of l.s. parameters = 149, R1 = 0.043 for 1999 reflections
with F0 > 4r(F0) and 0.047 for all 2147 reflections.
wR2 = 0.116, GOF = 0.999, restrained GOF = 0.999 for
all data (CCDC 282317).
6. (a) Grob, C. A.; Schiess, P. W. Angew. Chem., Int. Ed.
Engl. 1967, 6, 1–106; (b) Grob, C. A. Angew. Chem., Int.
Ed. Engl. 1969, 8, 535–622; (c) Sternbach, D.; Shibuya,
M.; Jaisli, F.; Bonetti, M.; Eschenmoser, A. Angew.
Chem., Int. Ed. Engl. 1979, 18, 634–636; (d) Fehr, C.;
Galindo, J.; Etter, O.; Thommen, W. Angew. Chem., Int.
Ed. 2002, 41, 4523–4526.
7. Mehta, G.; Kumaran, R. S. Tetrahedron Lett. 2003, 44,
7055–7059.
8. All new compounds were characterized on the basis of IR,
1H and 13C NMR and HRMS data. Spectral data for
24
selected compounds: (ꢀ)-16: ½aꢁD ꢀ170.4 (c 1.2, CHCl3);
11. We observed that whenever there was an E-double bond
present in the germacratrienes, as in 22, 38 and 40,
considerable line broadening and partial doubling of signals
were observed in the 1H NMR spectra due to the presence
of conformational isomers. Recording the spectra even at
(ꢀ50 °C) did not help much although reversible changes
were noticed. On the other hand, the 13C NMR spectra
were quite clean. Attributing the presence of conformers
to the Z-disubstituted double bond in the germacratrienes,
we also prepared the corresponding germacraenones
(iv–vi) from the saturated mesylates (i–iii), respectively.
IR 1702 cmꢀ1; H NMR (300 MHz, CDCl3): d 5.88 (ddt,
1
J = 10.5, 5.7, 1.8 Hz, 1H), 5.62–5.54 (m, 1H), 5.04 (t,
J = 8.4 Hz, 1H), 4.75 (s, 1H), 4.53 (s, 1H), 3.13 (td,
J = 5.4, 2.1 Hz, 1H), 3.09–3.00 (m, 2H), 2.86 (dd, J = 13.8,
10.2 Hz, 1H), 2.73 (m, 1H), 2.52 (dd, J = 14.1, 5.4 Hz,
1H), 2.25–2.19 (m, 2H), 2.06 (dd, J = 15.0, 2.4 Hz, 1H),
1.78 (s, 6H); 13C NMR (75 MHz, CDCl3): d 211.8, 147.2,
135.4, 130.7, 122.4, 121.8, 109.7, 44.1, 41.2, 39.8, 31.3,
28.5, 23.6, 22.4; HRMS (ES): m/z calcd for C14H20ONa
(M+Na): 227.1412; found: 227.1427. Compound (+)-22:
24
1
½aꢁD (+)-6.0 (c 1.0, CHCl3); IR 1704 cmꢀ1
;
13C NMR
Germacraenones (iv–vi) exhibited clean, clear cut H and
(75 MHz, CDCl3): d 210.2, 148.7, 133.0, 130.0, 129.7,
122.2, 109.4, 48.2, 47.5, 43.0, 39.4, 34.0, 21.1, 18.2; HRMS
(ES): m/z calcd for C14H20ONa (M+Na): 227.1412; found:
13C NMR spectra.
OMs
H
23
227.1418. Compound (ꢀ)-29: ½aꢁD ꢀ20.0 (c 0.8, CHCl3);
t
BuOK
IR 1701 cmꢀ1; H NMR (300 MHz, CDCl3): d 5.78 (ddt,
1
t
BuOH:THF (1:1)
J = 10.8, 5.4, 2.1 Hz, 1H), 5.34 (dd, J = 10.8, 5.4 Hz, 1H),
5.04 (t, J = 8.4 Hz, 1H), 4.76 (s, 1H), 4.51 (s, 1H), 3.35–
3.26 (m, 1H), 3.08 (dd, J = 15.3, 12.0 Hz, 1H), 2.97 (dd,
J = 13.5, 11.4 Hz, 1H), 2.74–2.66 (m, 1H), 2.38–2.22 (m,
2H), 2.14 (t, J = 6.0 Hz, 1H), 2.03 (dd, J = 15.3, 1.8 Hz,
1H), 1.78 (s, 6H), 1.23 (d, J = 7.2 Hz, 3H); 13C NMR
(75 MHz, CDCl3): d 215.2, 147.3, 135.4, 130.4, 128.9,
121.5, 109.8, 47.8, 40.9, 37.4, 31.8, 28.1, 23.6, 22.5, 18.8;
HRMS (ES): m/z calcd for C15H22ONa (M+Na):
o
O
O
0
C, 55%
OH
i
iv
v
OMs
H
t
BuOK
t
BuOH:THF (1:1)
0
o
C, 40%
OH
ii
OMs
H
23
241.1568; found: 241.1568. Compound (ꢀ)-34: ½aꢁD
t
BuOK
ꢀ326.7 (c 1.0, CHCl3); IR 1705 cmꢀ1
;
1H NMR
t
BuOH:THF (1:1)
o
(300 MHz, CDCl3): d 5.72 (dd, J = 17.4, 10.2 Hz, 1H),
5.57 (t, J = 10.2 Hz, 1H), 5.06 (t, J = 8.4 Hz, 1H), 4.75 (s,
0
C, 40%
O
OH
iii
vi