C O M M U N I C A T I O N S
a
Scheme 3
a
t
i
Conditions: (a) 1.5 equiv of MVK, 10 (5 mol %), 11 (20 mol %), neat, 4 °C; (b) Ph
2
PCH
2
CHdCH
SO , Et
Cl , -30 °C; (g) Hoveyda-Grubbs II (10 mol %), 0.0011
O; NMO, 4 Å MS, CH Cl ; TPAP; (j) 6.0 equiv of MePPh Br,
, 4 Å MS, MeCN; (l) Hg(OAc) , 1:1 acetone/H O; (m) Bu SnH, AIBN, C , 60 °C;
2
, BuLi, THF, -78 to 0 °C; Ti(O Pr)
4
, -78 °C; 9,
-
78 to 0 °C; MeI, 0 °C to rt; (c) LiTMP, THF, -78 °C; HMPA; MeOC(O)CN; (d) p-AcHNC
addition of diazo over 20 h; (f) 3.0 equiv of 5, MAD (15, 15 mol %), HNTf (10 mol %), CH
M, (CH Cl) , 80 °C, N sparge; (h) 10 equiv of NaBr, aq. DMF, 120 °C; (i) BH ·THF, Et
.0 equiv of NaHMDS, C , 80 °C; THF, 1.0 M HCl; (k) I , NaHCO
n) Ac O, DMAP, Et N, CH Cl
6
H
4
2
N
3
3
N, MeCN; (e) 14 (4 mol %), C
6
H
6
, reflux, slow
2
2
2
2
2
2
3
2
2
2
3
5
(
H
7 8
2
3
2
2
3
6 6
H
2
3
2
2
.
A double sequential oxymercuration with Hg(OAc)
2
was planned,
(6) Total and partial syntheses of cladiellins and related C2/C11-cembranoids
have been exhaustively reviewed recently. See: Ellis, J. M; Crimmins, M. T.
Chem. ReV. 2008, 108, 5278–5298.
9
in analogy with Kim’s synthesis, but only 10% of deacetylpoly-
anthellin A (19) was obtained using these conditions. Instead, a
three-step protocol involving iodoetherification, oxymercuration, and
(7) Ospina, C. A.; Rodriguez, A. D.; Ortega-Barria, E.; Capson, T. L. J. Nat.
Prod. 2003, 66, 357–363.
(
8) Bowden, B. F.; Coll, J. C.; Vasilescu, I. M. Aust. J. Chem. 1989, 42, 1705–
1726.
global reduction with Bu
:1 mixture of diastereomers. Both were acetylated and then
separated to provide (+)-1, which matched the reported spectral
3
SnH/AIBN was used to afford 19 as a
(
9) Kim, H.; Lee, H.; Kim, J.; Kim, S.; Kim, D. J. Am. Chem. Soc. 2006, 128,
6
1
5851–15855.
(10) Molander, G. A.; Czako, B.; St. Jean, D. J J. Org. Chem. 2006, 71, 1172–
7
-9
1180.
and optical rotation data,
in 15 linear steps from methallyl
(
11) (a) Pohlhaus, P. D.; Johnson, J. S. J. Am. Chem. Soc. 2005, 127, 16014–
alcohol.
16015. (b) Pohlhaus, P. D.; Johnson, J. S. J. Org. Chem. 2005, 70, 1057–
1
059. (c) Pohlhaus, P. D.; Sanders, S. D.; Parsons, A. T.; Li, W.; Johnson,
In summary, an expeditious route to the cladiellin hydroisoben-
zofuran core and (+)-1 is reported. Central to the completion of
J. S. J. Am. Chem. Soc. 2008, 130, 8642–8650. (d) Parsons, A. T.; Johnson,
J. S. J. Am. Chem. Soc. 2009, 131, 3122–3123.
this synthesis was the discovery that MADNTf
2
enables the [3+2]
(12) Hanson, R. M.; Sharpless, K. B. J. Org. Chem. 1986, 51, 1922–1925.
(
13) Klunder, J. M.; Onami, T.; Sharpless, K. B. J. Org. Chem. 1989, 54, 1295–
304.
(14) Shao, H.; Zhu, Q.; Goodman, M. J. Org. Chem. 1995, 60, 790–791.
cycloaddition of aldehydes and cyclopropanes containing labile
functionality. This should permit this methodology to be applied
to yet more complex systems.
1
(
(
(
15) Tanner, D.; Somfai, P. Tetrahedron 1986, 42, 5985–5990.
16) Chi, Y.; Gellman, S. H. Org. Lett. 2005, 7, 4253–4256.
17) Trace amounts of 5 were observed after extended reaction times (96 h)
with 5 mol % 10, but smooth addition occurred when 20 mol % 11 was
included.
18) Chen, K.; Baran, P. S. Nature 2009, 459, 786–787.
19) Ikeda, Y.; Ukai, J.; Ikeda, N.; Yamamoto, H. Tetrahedron 1987, 43, 723–
730.
Acknowledgment. We thank Prof. Deukjoon Kim for providing
an authentic synthetic sample of polyanthellin A. This research was
supported by the NSF (CHE-0749691) and Novartis (Early Career
Award to J.S.J.)
(
(
(
(
20) Mander, L. N.; Sethi, S. P. Tetrahedron Lett. 1983, 24, 5425–5428.
21) Yang, D.; Gao, Q.; Lee, C.-S.; Cheung, K.-K. Org. Lett. 2002, 4, 3271–
Supporting Information Available: Experimental procedures and
compound chacterization data. This material is available free of charge
via the Internet at http://pubs.acs.org.
3
274.
(22) Corey, E. J.; Myers, A. G. Tetrahedron Lett. 1984, 25, 3559–3562.
(
(
23) Boxer, M. B.; Yamamoto, H. Org. Lett. 2005, 7, 3127–3129.
24) Maruoka, K.; Itoh, T.; Sakurai, M.; Nonoshita, K.; Yamamoto, H. J. Am.
Chem. Soc. 1988, 110, 3588–3597.
References
2
(25) MADNTf was chosen because the cycloaddition proceeded with good
efficiency and selectivity without elimination of TMSOH from either 5 or
3. Lewis acids with nucleophilic counterions gave substantial ring opening
of 4. Complete catalyst optimization studies will be reported in a future
full paper.
(
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2
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