Total synthesis of (-)-callipeltoside A

Article abstract of DOI:10.1021/jo101598y

A total synthesis of (-)-callipeltoside A (1) has been achieved. The core macrocycle was made via a dual macrolactonization/pyran hemiketal formation reaction, developed to circumvent issues related to the reversible nature of acylketene formation from β-

Full text of DOI:10.1021/jo101598y

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Total Synthesis of (-)-Callipeltoside A
Thomas R. Hoye,* Michael E. Danielson, Aaron E. May, and Hongyu Zhao
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
hoye@umn.edu
Received August 14, 2010
A total synthesis of (-)-callipeltoside A (1) has been achieved. The core macrocycle was made via a
dual macrolactonization/pyran hemiketal formation reaction, developed to circumvent issues related
to the reversible nature of acylketene formation from β-keto lactone substrates. Initial approaches to
the core of the natural product that revolved around ring-closing metathesis (RCM) and relay ring-
closing metathesis (RRCM) reactions are also described.
Introduction
C(20)/C(21) as well as the overall absolute configuration of
(-)-callipeltoside A (1) was reported by the Trost laboratories
in 2002.3a Additional total syntheses have been reported,3b-g
and numerous related studies have appeared.4
Callipeltoside A (1) is a cytotoxic macrolide isolated in 1996
from the marine lithistida sponge (Callipelta sp.).1 The stereo-
chemical features of callipeltoside A were deduced on the basis
of extensive NMR studies. When we initiated the research
described here, issues still remained with respect to (i) the
absolute configuration and (ii) the relative configuration of
Results and Discussion
Our approach to 1 involved a convergent union of the three
key intermediates: macrolactone 2, carbohydrate 3, and phos-
phonate 4 (Scheme 1). Our initial approach to the synthesis of
2 aimed to utilize a RCM reaction from a suitable precursor,
such as 5.5 Unfortunately, neither 5 or its C(13) epimer (epi-5)
could be ring-closed to give a macrocyclic product (Scheme 2).
Using Grubbs’ first-generation metathesis initiator (7),6 no
initiation was observed at room temperature, as evidenced
by lack of styrene formation by analysis of the NMR spec-
trum and recovery of starting material. Attempts to alter the
reactivity of the substrate by using a more constrained, and
perhaps geometrically favorable, conformer (cf. 6) also
ꢀ
C(13) and C(20)/C(21) vis-a-vis those in the remainder of the
molecule. The relative configuration of C(13) was established
by Paterson and co-workers.2 The first total synthesis, which
established the remaining relative configurational issues of
(1) (a) Zampella, A.; D’Auria, M. V.; Minale, L.; Debitus, C.; Roussakis,
C. J. Am. Chem. Soc. 1996, 118, 11085–11088. (b) Zampella, A.; D’Auria, V.;
Minale, L. Tetrahedron 1997, 53, 3243–3248.
(2) Paterson, I.; Davies, R. D. M.; Marquez, R. Angew. Chem., Int. Ed.
2001, 40, 603–607.
(3) Total syntheses: (a) Trost, B. M.; Dirat, O.; Gunzner, J. L. Angew.
Chem., Int. Ed. 2002, 41, 841–843. (b) Evans, D. A.; Hu, J.; Burch, J. D.;
Jaeschke, G. J. Am. Chem. Soc. 2002, 124, 5654–5655. (c) Trost, B. M.;
Gunzner, J. L.; Dirat, O.; Rhee, Y. H. J. Am. Chem. Soc. 2002, 124, 10396–
10415. (d) Paterson, I.; Davies, R. D. M.; Heimann, A. C.; Marquez, R.;
Meyer, A. Org. Lett. 2003, 5, 4477–4480. (e) Huang, H.; Panek, J. S. Org.
Lett. 2004, 6, 4383–4385. (f) Evans, D. A.; Burch, J. D.; Hu, E.; Jaeschke, G.
Tetrahedron 2008, 64, 4671–4699. (g) Carpenter, J.; Northrup, A. B.; Chung,
D.; Wiener, J. J. M.; Kim, S.-G.; MacMillan, D. W. C. Angew. Chem., Int.
Ed. 2008, 47, 3568–3572.
(4) For a recent compilation of approaches to the synthesis of the
macrolactone fragment, see ref 3f.
(5) (a) Hoye, T. R.; Zhao, H. Org. Lett. 1999, 1, 169–171. (b) Zhao, H. Ph.
D. Thesis, University of Minnesota, 2000.
(6) Schwab, P.; France, M. B.; Ziller, J. W.; Grubbs, R. H. Angew. Chem.,
Int. Ed. 1995, 34, 2039–2041.
7052 J. Org. Chem. 2010, 75, 7052–7060
Published on Web 10/08/2010
DOI: 10.1021/jo101598y
r
2010 American Chemical Society

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SCHEME 1. Callipeltoside Retrosynthesis
SCHEME 2. RCM Substrates
SCHEME 3. Relay Ring-Closing Metathesis
failed.7 At elevated temperatures (50-70 °C, benzene sol-
vent) the catalyst [either 7 or the second generation initiator
(8)]8 decomposed and starting material (5 and 6) could be
recovered.
Believing that the main problem with the lack of reactivity of
substrates 5 and 6 was due to slow initiation, we hypothesized
that the use of a relay strategy would be advantageous.5b,9 The
concept, outlined in Scheme 3, was to use allyloxymethyl relays
on substrates 9 and 10. Ruthenium loading onto the terminal
alkene of the relay was envisioned to give intermediates 11 and
12. Intramolecular cyclization of each would give 13 or 14,
respectively, with concomitant formation of 3,4-dihydrofuran.
Finally, cyclization of 13 and 14 would give the desired β-keto
lactone 15 and regenerate a ruthenium methylidene as the
active catalyst. Since we had no way of knowing whether inter-
mediate 13 or 14 would be more likely to macrocyclize, we
chose to undertake the synthesis of both substrates 9 and 10.
The synthesis of relay substrate 9 is outlined in Scheme 4.
Known Weinreb amide 16 was protected as a PMB ether
using PMB-trichloroacetimidate and catalytic CSA.10 Hy-
droboration/oxidation (9-BBN), followed by TBS protec-
tion and DIBAL-H reduction of the Weinreb amide gave
aldehyde 17. Lithium-halogen exchange of alkenyl iodide 18
followed by addition to aldehyde 17 gave a 1:1.5 ratio of
newly formed secondary alcohols. Subsequent methylation
with methyl iodide gave the relay-armed substrate 19. De-
protection of the primary TBS ether using TBAF, oxidation
with Dess-Martin periodinane, vinylogous Mukaiyama
aldol reaction with diene 20,11 and TMS protection gave
dioxinone substrate 21. Refluxing this substrate in benzene
(7) Danielson, M. E. Ph.D. Thesis, University of Minnesota, 2003.
(8) Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Org. Lett. 1999,
1, 953–956.
(9) (a) Hoye, T. R.; Jeffrey, C. S.; Tennakoon, M. A.; Wang, J.; Zhao, H.
J. Am. Chem. Soc. 2004, 126, 10210–10211. (b) Wang, X.; Bowman, E. J.;
Bowman, B. J.; Porco, J. A. Angew. Chem., Int. Ed. 2004, 43, 3601–3605.
(c) Hoye, T. R.; Jeon, J. Methathesis Involving a Relay and Applications in
Natural Product Synthesis. In Metathesis in Natural Product Synthesis;
Cossy, J., Arseniyadis, S., Meyer, C., Eds.; Wiley-VCH: Weinheim, 2010;
pp 261-285.
(10) Schoening, K. U.; Wittenberg, R.; Kirschning, A. Synlett 1999, 10,
1624–1626.
(11) Sato, M.; Sugita, Y.; Abiko, Y.; Kaneko, C. Tetrahedron: Asymme-
try 1992, 3, 1157–1160.
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SCHEME 4. Synthesis of Relay Substrate 9a
SCHEME 5. Synthesis of Relay Substrate 10a
aKey: (a) allyl bromide, NaH, 81%; (b) tBuLi, CuI, 24; (c) vinylMgBr,
dr = 1:1; SiO2 separation; 34%/34%; (d) MeI, NaH, DMF, 89%;
(e) TBAF, THF, 87%; (f) DMP, 92%; (g) 20, BF3 OEt2, 90%; (h) TMSCl,
TEA, 65%; (i) 25, benzene reflux; (j) PPTS, ACN, 77% over two steps.
3
aKey: (a) PMB acetimidate, CSA, 92%; (b) 9-BBN, then NaOH/H2O2,
56%; (c) TBSCl, TEA, 60%; (d) DIBAL-H, 95%; (e) BuLi, then 18,
t
SCHEME 6. Truncation of Relay Substrate 10
dr = 1:1.5; SiO2 separation; 22%/33%; (f) MeI, NaH, DMF, 64%;
(g) TBAF, THF; (h) DMP; (i) 20, BF3 OEt2; (j) TMSCl, 65% over four
steps; (k) 22, benzene reflux; (l) PPTS, ACN 69% over two steps.
3
with secondary alcohol 22,12 followed by TMS deprotection
with PPTS in acetonitrile gave 9.
The synthesis of the alternative relay substrate 10 is out-
lined in Scheme 5. The allyl ether of known bromo alkene
2313 was used, after lithium-halogen exchange (cat. CuI), to
ring-open the TBS protected epoxide 2414 to give relay-armed
alcohol 25. Aldehyde 17 was elaborated by addition of vinyl
magnesium bromide, giving a separable mixture of diastereo-
meric (dr 1:1) alcohols. Methylation with methyl iodide, TBAF
deprotection, and oxidation with Dess-Martin periodinane
gave aldehyde 26. The vinylogous Mukaiyama aldol reaction of
26 with diene 20 and TMS protection of the C(5)-hydroxyl gave
dioxinone 27. Refluxing a mixture of alcohol 25 and dioxinone
27 in benzene, followed by TMS deprotection, gave relay
substrate 10.
Unfortunately, subjection of either 9 or 10 to the metath-
esis initiator 8 did not lead to the formation of desired
product 15 but instead gave 5, the substrate for the initial
RCM study. The process leading to 5 is outlined in Scheme 6,
an event we refer to as truncation. When metathesis initiator 8
reacts with 10, the relay to produce 28 presumably proceeds as
planned, as evidenced by formation of 3,4-dihydrofuran (1H
NMR). In order for macrocyclic ring closure to occur within
28, the rate of its intramolecular cyclization (kintra) must be
faster than the rate of bimolecular attack on the more reactive
alkene in another molecule of 10 (kinter). Since truncation is
bimolecular, we recognized that running the reaction at higher
dilution would result in a more favorable kintra/kinter ratio, but
even at 10-5 M, only the truncation product 5 was observed.7
We examined other ways to favorably bias the ratio of
kintra to kinter during this RRCM reaction. Since disubstitut-
ed alkenes are slower to engage in cross-metathesis (CM), it
was hoped that using a 1,1-disubstituted alkene within the
relay arm would slow the bimolecular truncation rate suffi-
ciently so that macrocyclization could prevail. To this end,
substrates 29 and 30 (Scheme 7) were synthesized in an ana-
logous manner. While our reasoning was apparently sound, as
evidenced by a significantly slower overall rate of reaction, no
desired product was formed using these substrates having the
modified relay subunit. Instead the truncation products 5 and 6
were observed, respectively. The clear implication is that the
initial relay event occurred to deliver ruthenium to the more
hindered carbon atom of the otherwise inactive alkene. As these
results illustrate, the use of a RRCM strategy by no means
guarantees a successful outcome. If the inherent rate of the
crucial metathesis cyclization event is slower than competing
events (e.g., CM or [Ru] decomposition), as is the case here, then
(12) Guo, J.; Duffy, K. J.; Stevens, K. L.; Dalko, P. I.; Roth, R. M.;
Hayward, M. M.; Kishi, Y. Angew. Chem., Int. Ed. 1998, 37, 187–192.
(13) Corey, E. J.; Bock, M. G.; Kozikowski, A. P.; Rama Rao, A. V.;
Floyd, D.; Lipshutz, B. Tetrahedron Lett. 1978, 19, 1051–1054.
(14) Schaus, S. E.; Brandes, B. D.; Larrow, J. F.; Tokunaga, M.; Hansen,
K. B.; Gould, A. E.; Furrow, M. E.; Jacobsen, E. N. J. Am. Chem. Soc. 2002,
124, 1307–1315.
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SCHEME 8. Synthesis of Lactonization Precursor 38a
SCHEME 7. Additional RRCM Substrates
the cyclization will not be efficient regardless of the process by
which the key ruthenium alkylidene intermediate is formed.9c
We then turned to a strategy in which the Boeckman
lactonization15 of an acylketene intermediate would be used
to close the core macrocycle.5b This strategy formed the
bases of both the Trost synthesis of 13a,c and the Marshall
synthesis16 of the aglycon. Reaction of the TBS-protected
epoxide 31 with lithium TMS-acetylide, followed by a two-
step deprotection gave diol 32.17,18 Negishi carboalumina-
tion/iodination19 and sequential protection of the 1,2-diol
as TBS and PMB ethers gave 33. Lithium-halogen exchange
in 33 and addition to aldehyde 34 gave a 1:1 mixture of
separable secondary alcohols.20 Recycling of the undesired
epimer by oxidation with Dess-Martin periodinane, followed
by reduction with lithium triethylhydridoborate gave the de-
sired epimer in a 10:1 dr. Subsequent methylation gave alkene
35, which was subjected to hydroboration/oxidation (9-BBN).
The resulting primary alcohol was subjected to Dess-Martin
periodinane oxidation and vinylogous Mukaiyama aldol reac-
tion with diene 20. Each of the two new stereocenters at C(5)
and C(6) were formed with essentially full diastereocontrol.
Protection of the C(5)-OH with MOMCl and PMB removal at
C(13) with DDQ gave the lactonization precursor 36.
aKey: (a) Li-TMS-acetylide, BF3 OEt2; (b) K2CO3, MeOH; (c) KF,
MeOH reflux, 77% over three steps; (d) AlMe3, ZrCp2Cl2; I2, 65%;
(e) TBSCl, imidazole, 72%; (f) PMB acetimidate, CSA, 82%; (g) n-BuLi,
34, dr = 1:1; (h) MeI, NaH, 80%; (i) 9-BBN, then NaOH/H2O2, 99%;
3
(j) DMP, 79%; (k) 20,BF3 OEt2, 70%; (l) MOMCl, 95%; (m) DDQ, 100%.
3
SCHEME 9. Boeckman Cyclization and Competitive
Hydrolysis of 36
The dioxinone-containing substrate 36 was heated in
refluxing toluene to effect thermal extrusion of acetone and
concomitant generation of the acylketene 37. Macrolactoni-
zation involves cylization of the C(13) hydroxyl group to give
enol 38 (Scheme 8). Two products were isolated: the keto
lactone 39 and the methyl ketone 40 (64% and 15%,
respectively) (Scheme 9). The latter arises from competitive
addition of water to 37 and subsequent decarboxylation of
the resulting β-keto acid, a phenomenon that has been
observed by others.21 The relative amount of 40 increased
over time. This suggests that the unimolecular lactonization
of the acylketene 37 outcompetes its trapping by water and
that the ketolactone 39 is able to revert via 38 to acylketene
37.22 While concentration effects are undoubtedly also im-
portant, it is relevant that (i) addition of an O-H bond to an
acylketene is a concerted event (cf. 37 to 38)23 and (ii) the
O-H bond dissociation energyofwater issubstantially higher
than those of alcohols (119 vs 104-107 kcal mol-1).24 We
hypothesized that the detrimental outcome of competitive
water addition could be mitigated if the β-ketone in a macro-
lactone like 39 could be sequestered. An attractive possibility
was that it be trapped as its corresponding pyran hemiketal by
a free hydroxyl group at C(7).22
(15) Boeckman, R. K., Jr.; Pruitt, J. R. J. Am. Chem. Soc. 1989, 111,
8286–8288.
(16) Marshall, J. A.; Eidam, P. M. Org. Lett. 2008, 10, 93–96.
(17) Smith, A. B., III; Verhoest, P. R.; Minbiole, K. P.; Schelhaas, M.
J. Am. Chem. Soc. 2001, 123, 4834–4836.
To test this idea, we elected to prepare diol 43 (Scheme 10).25
Thus, the vinyllithium species derived from ent-33 was added
to aldehyde 41 to give a 1:1 ratio of diols. Separation and methyl-
ation with methyl iodide gave alkene 42. Hydroboration/
oxidation, Dess-Martin oxidation, and vinylogous Mukaiyama
(18) Jones, E. R. H.; Stephenson, J. S.; Turner, W. B.; Whiting, M. C.
J. Chem. Soc. 1963, 2048–2055.
(19) Rand, C. L.; Van Horn, D. E.; Moore, M. W.; Negishi, E. J. Org.
Chem. 1981, 46, 4096–4097.
(20) Smith, A. B.; Barbosa, J.; Wong, W.; Wood, J. L. J. Am. Chem. Soc.
1996, 118, 8316–8328.
(21) Boeckman, R. K., Jr.; Shao, P.; Wrobleski, S. T.; Boehmler, D. J.;
Heintzelman, G. R.; Barbosa, A. J. J. Am. Chem. Soc. 2006, 128, 10572–
10588.
(23) (a) Freiermuth, B.; Wentrup, C. J. Org. Chem. 1991, 56, 2286–2289.
(b) Birney, D. M.; Wagenseller, P. E. J. Am. Chem. Soc. 1994, 116, 6262–
6270.
(24) Blanksby, S. J.; Ellison, G. B. Acc. Chem. Res. 2003, 36, 255–263.
(25) By this juncture, the configuration at C(13) in 1 had been
established,2 so our subsequent studies described here all involved inter-
mediates directed toward the 13R configuration.
(22) Hoye, T. R.; Danielson, M. E.; May, A. E.; Zhao, H. Angew. Chem.,
Int. Ed. 2008, 47, 9743–9746.
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SCHEME 10. Synthesis of Dual Macrolactonizion/Pyran-
SCHEME 12. Completion of the Synthesisa
Hemiketal Precursor 43a
aReagents and conditions: (a) TBAF, THF; (b) TMSCl, TEA, DCM;
(c) NaHCO3, MeOH, 70% over three steps; (d) SO3 pyr, DMSO, TEA;
(e) 4, LiHMDS, THF; (f) TBAF, THF, 54% over three steps; (g) 5,
TMSOTf, DCM, 70%.
3
aReagents and conditions: (a) n-BuLi, ent-33; then 41, dr = 1:1, SiO2
separation, 34%/34%; (b) MeI, NaH, 80%; (c) 9-BBN, then NaOH/
H2O2, 70%; (d) DMP, 76%; (e) 20, BF3 OEt2, 90%; (f) TMSCl;
3
of the TMS ether at C(5). Glycosidation3a with known
acetimidate 327 provided (-)-callipeltoside A (1).
(g) DDQ, 78% over two steps.
In conclusion, we have completed a total synthesis of (-)-
callipeltoside A (1). Initial attempts using an RCM reaction
on substrates 5 and 6 were not successful; presumably, these
compounds are simply too hindered to load ruthenium to the
requisite (and more hindered) alkene carbon atom. This led
to the evolution of the RRCM strategy, which was explored
via substrates 9, 10, 29, and 30. In each case, relay activation
allowed ruthenium to be transiently installed to the necessary
site (cf. 13, 14, and 28), but bimolecular truncation of these
species thwarted the (inherently slow) final ring-closing event.
Ultimately, the synthesis of 1 (21 linear steps from TBS-
glycidol 24, 0.7% yield) was enabled by a highly efficient
acylketene mediated dual macrolactonization/pyran-hemiketal
formation reaction, converting the linear precursor 43 directly
to the bridged bicyclic macrolactone 44.
SCHEME 11. Formation of Pyran-Hemiketal 44
Experimental Section
General Methods. 1H NMR chemical shifts in CDCl3 are
referenced to TMS (0.00 ppm) and in PhH-d6 to 7.16. 13C NMR
chemical shifts in CDCl3 are referenced to chloroform (77.2
ppm). The following format has been used to report peaks:
chemical shift in ppm [multiplicity, coupling constant(s) in Hz,
integral]. MPLC refers to medium-pressure liquid chromatog-
raphy (25-60 psi) using hand-packed columns of E. Merck
silica gel (230-400 mesh), a pump, and a differential refractive
index detector. Reactions requiring anhydrous conditions were
performed under an atmosphere of nitrogen or argon in oven-
dried glassware. Dry diethyl ether and benzene were distilled
from sodium benzophenone ketyl. Toluene was distilled from
Na/K. Anhydrous THF and methylene chloride were passed
through a column of activated alumina. Triethylamine and
pyridine were distilled from KOH just prior to use. DMF was
aldol reaction with diene 20 was performed. Protection of the
resulting secondary alcohol, followed by DDQ removal of
both PMB ethers afforded the dioxinone diol 43.
To our delight, when refluxed in benzene for 12 h, dioxi-
none 43 produced the desired dual macrocyclic pyran hemi-
ketal 44 in 76% yield (Scheme 11). We suspect that pyran
hemiketal formation within either enol 46 or ketone 47
follows macrolactonization (45 to 46). It is noteworthy that
no products indicative of competitive trapping of the acyl-
ketene 45 by water could be detected (and no 8-membered
lactone from reaction of the C(7)-OH with the ketene carbon
was observed). It is clear that in situ protection of the C(3)-
ketone as its hemiketal is advantageous.22
˚
stored over 4 A molecular sieves. The structure of each inter-
mediate numbered here as S## can be found in the Supporting
Information.
(þ)-(2S)-4-Pentyne-1,2-diol (32)28. To epoxide 31 (13.3 g, 71.0
mmol), TMS-acetylene (15 mL, 106.0 mmol), and THF (141
mL) was added n-BuLi (3.2 M in hexanes, 40.0 mL, 92.0 mmol)
The completion of the synthesis, following established
lines, is outlined in Scheme 12. A three-step protecting group
manipulationwasusedtoconvert44into48. Parikh-Doering
oxidation afforded the corresponding aldehyde, from which
aglycon 49 was obtained by Horner-Emmons olefination
with the known phosphonate 4,26 followed by deprotection
dropwise at -78 °C, followed by BF3 OEt2 (13.4 mL, 106.0
3
mmol) dropwise at the same temperature. The solution was
stirred for 45 min at -78 °C before being quenched with aqueous
NH4Cl (20 mL). The mixture was allowed to warm to rt and
(27) Evans, D. A.; Hu, E.; Tedrow, J. S. Org. Lett. 2001, 3, 3133–3136.
(28) (a) Heathcock, C. H.; McLaughlin, M.; Medina, J.; Hubbs, J. L.;
Wallace, G. A.; Scott, R.; Claffey, M. M.; Hayes, C. J.; Ott, G. R. J. Am.
Chem. Soc. 2003, 125, 12844–12849. (b) Tang, B.; Bray, C. D.; Pattenden, G.
Tetrahedron Lett. 2006, 47, 6401–6404. (c) Ding, F.; Jennings, M. P. J. Org.
Chem. 2008, 73, 5965–5976.
(26) Chlorocyclopropane side chain syntheses: (a) Olivo, H. F.;Velazquez,
F.; Trevisan, H. C. Org. Lett. 2000, 2, 4055–4058. (b) Evans, D. A.; Burch, J. D.
Org. Lett. 2001, 3, 503–505.
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Hoye et al.
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diluted with H2O (150 mL). The aqueous layer was extracted
with DCM (3 ꢀ 100 mL), and the combined organic portions
were dried over Na2SO4 and concentrated to give crude TMS
alkyne as a colorless oil. This alkyne was immediately subjected
to desilylation. To the crude oil were added K2CO3 (29.3 g,
212 mol) and MeOH (100 mL), and this mixture was stirred for
24 h at rt. The suspended K2CO3 was filtered through Celite on a
sintered glass funnel with MeOH. The filtrate was concentrated
to afford the crude alkyne as a mixture of primary and second-
ary TBS ethers. The crude products were carried into the next
step without purification. To the mixture of alkynes were added
MeOH (40 mL), THF (40 mL), and KF (24 g, 420 mmol); and
the resulting slurry was refluxed at 65 °C for 48 h. The mixture
was cooled to rt, concentrated, placed on a flash column, and
purified via flash chromatography (hexanes/EtOAc = 1:1
followed by 100% EtOAc) to provide a pale yellow oil that
crystallized in a freezer overnight to afford diol 32 as white
needles (3.2 g, 77%): 1H NMR (300 MHz, CDCl3) δ 3.91 (dddd,
J = 3.7, 6.2, 6.2, and 6.2 Hz, 1H), 3.77 (dd, J = 3.7 and 11.1 Hz,
1H), 3.62 (dd, J = 6.2 and 10.0 Hz, 1H), 2.45 (dd, J = 2.7 and
6.2 Hz, 2H), 2.35 (bs, 1H), 1.90 (bs, 1H), 2.08 (t, J = 2.7 Hz, 1H);
13C NMR (125 MHz, CDCl3) δ 80.3, 70.7, 70.2, 65.3, 23.2;
GC-MS tR = 2.66 min; m/z 100, 69, 61; IR (neat) 3300, 3292,
2113, 1719, 1416, 1085, 1044 cm-1; mp 44-51 °C; TLC Rf =
0.35, 100% EtOAc; [R]rt þ8.22 (c = 1.1, CHCl3).
(-)-[3S-(3R*,4S*,5S*,9S*),6E]-5-Methoxy-3,9-bis[(4-methoxy-
phenyl)methoxy]-2,4,7-trimethyl-10-[[(1,1-dimethylethyl)dimethyl-
silyl]oxy]-1,6-decadiene (42). To vinyl iodide ent-33 (600 mg, 1.26
mmol, prepared by the same sequence described above) and
diethyl ether (10 mL, stirred over CaH2 for 1 h) in a round-bottom
flask was added solid CaH2 (5 mg), and the mixture was stirred for
10 min at rt. The cloudy solution was cooled to -78 °C, n-BuLi
(2.1 M in hexane, 0.66 mL, 1.38 mmol) was added dropwise, and
the mixture was stirred for 10 min. At the same temperature,
aldehyde 4129 (342 mg, 1.38 mmol) in diethyl ether (2 mL) was
added to the flask by cannula, and the solution was stirred for
15 min before warming to 0 °C. The reaction mixture was poured
into a separatory funnel containing aqueous NH4Cl, diluted with
water, and extracted with DCM. The combined organic layers
were dried over Na2SO4, concentrated, and purified by MPLC
(hexanes/EtOAc = 7:3) to afford (-)-[3S-(3R*,4S*,5S*,9S*),6E]-
10-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-3,9-bis-[(4-methoxyph-
enyl)methoxy]-2,4,7-trimethyldeca-1,6-dien-5-ol (S30, 255 mg,
34%) and its C5-epimer (S30b, 265 mg, 34%), each as a colorless
oil. S30: 1H NMR (500 MHz, CDCl3) δ 7.27 (d, J = 8.8 Hz, 2H),
7.24 (d, J = 8.7 Hz, 2H), 6.88 (d, J = 8.8 Hz, 2H), 6.84 (d, J = 8.8
Hz, 2H), 5.23 (broad d, J = 8.4 Hz, 1H), 5.03 (s, 1H), 5.00 (s, 1H),
4.59 (d, J = 11.4 Hz, 1H), 4.52 (d, J = 11.2 Hz, 1H), 4.49 (d, J =
11.2 Hz, 1H), 4.29 (ddd, J = 4.6, 7.3, and 9.0 Hz, 1H), 4.21 (d, J =
11.4 Hz, 1H), 4.00 (d, J = 4.0 Hz, 1H), 3.79 (s, 3H), 3.77 (s, 3H),
3.54 - 3.69 (m, 3H), 2.25 (dd, J = 4.3 and 13.9 Hz, 1H), 2.18 (dd,
J = 7.7 and 13.9 Hz, 1H), 2.18 (d, J = 4.6 Hz, 1H), 1.73 (ddq, J =
4.3, 7.2, and 7.2 Hz, 1H), 1.70 (s, 3H), 1.66 (s, 3H), 0.90 (s, 9H),
0.82 (d, J = 7.1 Hz, 3H), 0.05 (s, 6H); 13C NMR (125 MHz,
CDCl3) δ 159.2, 159.0, 142.8, 135.7, 131.0, 130.6, 129.5, 129.2,
113.8, 113.6, 112.5, 82.0, 78.1, 71.7, 70.4, 70.3, 65.6, 55.2, 42.1,
41.3, 25.9, 19.5, 18.3, 17.2, 10.7, -5.31, -5.38; IR (neat) 3476,
2952, 2928, 2856, 1613, 1514, 1248, 1090, 1037, 836 cm-1; HRMS
(FAB) calcd for (C35H54O6Si þ Na)þ 621.3582, found 621.3593;
TLC Rf = 0.3 in hexanes/EtOAc 4:1 [R]rt -10.31 (c = 0.38,
DCM). S30b: 1H NMR (500 MHz, CDCl3) δ 7.26 (d, J = 8.2 Hz,
2H), 7.25 (d, J = 9.0 Hz, 2H), 6.87 (d, J = 8.2 Hz, 2H), 6.86 (d,
J = 9.0 Hz, 2H), 5.37 (broad d, J = 8.2 Hz, 1H), 5.07 (s, 1H), 5.04
(s, 1H), 4.61 (d, J = 11.2 Hz, 1H), 4.50 (d, J = 11.2 Hz, 1H), 4.49
(d, J = 11.2 Hz, 1H), 4.44 (ddd, J = 2.9, 2.9, and 8.2, 1H), 4.19 (d,
J = 11.2 Hz, 1H), 3.83 (d, J = 5.6 Hz, 1H), 3.81 (s, 3H), 3.79 (s,
3H), 3.53-3.66 (m, 3H), 2.25 (dd, J = 5.1 and 13.9 Hz, 1H), 2.17
(d, J = 2.9, 1H), 2.16 (dd, J = 7.2 and 13.9 Hz, 1H), 1.73 (ddq,
J = 3.0, 5.6, and 6.9 Hz, 1H), 1.70 (s, 3H), 1.57 (s, 3H), 0.97 (d,
J = 7.3 Hz, 3H), 0.90 (s, 9H), 0.05 (s, 6H); 13C NMR (125 MHz,
CDCl3) δ159.1, 159.0, 142.6, 134.8, 131.0, 130.5, 129.4, 129.3, 129.2,
113.8, 113.7, 113.4, 85.6, 78.4, 71.8, 70.7, 70.3, 65.6, 55.2, 41.9, 41.0,
25.9, 18.5, 18.3, 17.3, 8.0, -5.31, -5.38; IR (neat) 3476, 2952, 2928,
2855, 1612, 1513, 1464, 1247, 1081, 1037, 836 cm-1; TLC Rf = 0.3 in
hexanes/EtOAc 4:1; [R]rt -34.06 (c = 0.31, DCM).
(-)-(2S,4E)-1-[[(1,1-Dimethylethyl)dimethylsilyl]oxy]-5-iodo-
2-[(4-methoxyphenyl)methoxy]-4-methyl-4-pentene (33). To zir-
conocene dichloride (2.5 g, 9.6 mmol) and 1,2-dichloroethane
(90 mL) was added AlMe3 (2.0 M in toluene, 36 mL, 72 mmol)
dropwise at rt followed by diol 32 (2.4 g, 24 mmol) in 1,2-
dichloroethane (20 mL). The solution was stirred at 50 °C for
48 h and then cooled to -40 °C. Iodine (9.1 g, 36 mmol) in THF
(26 mL) was added dropwise by cannula. The resulting dark
brown solution was allowed to warm and was stirred for 30 min at
rt before being poured into a mixture of hexanes and sodium
potassium tartrate. The aqueous layer was extracted with EtOAc
(1 ꢀ 50 mL), saturated with NaCl, and extracted again with
EtOAc (3 ꢀ 50 mL). The combined organic layers were dried
over Na2SO4, concentrated, and chromatographed (100%
EtOAc) to provide iodo diol (Rf = 0.13 in 1:1 hexanes/EtOAc) as
a pale yellow oil (3.4 g, 58%). The diol (3.0 g, 12.4 mmol) was
dissolved in DCM (120 mL) and treated with TEA (7.0 mL, 50.0
mmol), DMAP (230 mg 1.86 mmol), and TBSCl (3.0 g 20.0
mmol). The resulting solution was stirred 24 h at rt before being
quenched with aqueous NH4Cl (50 mL), diluted with H2O
(100 mL), and extracted with DCM. The combined organic layers
were dried over Na2SO4, concentrated, and chromatographed
(hexanes/EtOAc = 19:1) to provide a primary TBS ether (Rf =
0.25 in 9:1 hexanes/EtOAc) as a colorless oil (3.2 g, 72%). To
this ether (310 mg, 0.87 mmol) in DCM (5 mL) were added
p-methoxybenzyl trichloroacetimidate (762 mg, 2.7 mmol) and
CSA (46 mg, 0.2 mmol). The reaction mixture was stirred for 48 h
before being quenched with aqueous NaOH (10%, 20 mL). The
mixture was extracted with DCM, washed with aqueous NaOH
(10%, 20 mL), dried over MgSO4, and concentrated. Purification
by MPLC (hexanes/EtOAc = 12:1) gave 33 (330 mg, 82%) as a
colorless oil: 1H NMR (500 MHz, CDCl3) δ 7.23 (d, J = 8.5 Hz,
2H), 6.89 (d, J = 8.5 Hz, 2H), 5.97 (broad s, 1H), 4.60 (d, J = 11.5
Hz, 1H); 4.46 (d, J = 11.0 Hz, 1H), 3.81 (s, 3H), 3.67 (m, 1H), 3.55
(dd, J = 5.0 and 8.5 Hz, 1H), 3.52 (dd, J = 5.5 and 8.5 Hz, 1H),
2.44 (dd, J = 3.5 and 14.0 Hz, 1H), 2.36 (dd, J = 8.0 and 13.0 Hz,
1H), 1.78 (broad s, 3H), 0.90 (s, 9H), 0.06 (s, 6H); 13C NMR (125
MHz, CDCl3) δ 159.2, 144.9, 130.6, 129.5, 113.8, 77.2, 77.1, 72.0,
65.0, 55.3, 41.8, 25.9, 24.3, 18.3, -5.32, -5.37; IR (neat) 3063,
3032, 2996, 2958, 2931, 2857, 1612, 1512, 1250 cm-1; GC-MS
To alcohol S30 (300 mg, 0.502 mmol) in DMF (3 mL) were
added MeI (0.37 mL, 6.00 mmol) and NaH (25% dispersion in
mineral oil, 240 mg, 2.51 mmol) at rt. The mixture was stirred for
24 h, quenched with aqueous NH4Cl (10 mL), diluted with H2O,
extracted with Et2O (3 ꢀ 10 mL), washed with H2O, and dried
over Na2SO4. MPLC (hexanes/EtOAc = 19:1) separation gave
42 (245 mg, 80%) as a colorless oil: 1H NMR (500 MHz, CDCl3)
δ 7.27 (d, J = 8.6 Hz, 2H), 7.24 (d, J = 8.6 Hz, 2H), 6.88 (d, J =
8.6 Hz, 2H), 6.84 (d, J = 8.6 Hz, 2H), 5.06 (broad d, J = 9.7 Hz,
1H), 4.98 (app s, 2H), 4.60 (d, J = 11.8 Hz, 1H), 4.50 (d, J = 11.8
Hz, 1H), 4.50 (d, J = 11.3 Hz, 1H), 4.19 (d, J = 11.3 Hz, 1H),
4.00 (d, J = 3.9 Hz, 1H), 3.80 (s, 3H), 3.79 (dd, J = 8.4 and 9.4
Hz, 1H), 3.78 (s, 3H), 3.57-3.69 (m, 3H), 3.07 (s, 3H), 2.30 (dd,
J = 4.6 and 14.0 Hz, 1H), 2.23 (dd, J = 6.7 and 14.0 Hz, 1H),
1.73 (ddq, J = 3.9, 8.4, and 7.0 Hz, 1H), 1.68 (app s, 6H), 0.90 (s,
9H), 0.75 (d, J = 7.1 Hz, 3H), 0.05 (s, 6H); 13C NMR (125 MHz,
t
R = 12.6 min; m/z 419, 349, 121; HRMS (CI, 4% NH3 in CH4)
calcd for (C20H33IO3Si þ NH4)þ 494.1582, found 494.1579; TLC
Rf = 0.3, hexanes/EtOAc = 15:1; [R]rt -15.3 (c = 1.0, CHCl3).
(29) Hoffman, R. W.; Stuermer, R. Chem. Ber. 1994, 127, 2511–2518.
J. Org. Chem. Vol. 75, No. 21, 2010 7057

Hoye et al.
JOCFeatured Article
CDCl3) δ 159.0, 158.9, 143.5, 137.8, 131.5, 131.0, 129.3, 129.2,
126.8, 113.65, 113.62, 111.6, 81.2, 78.3, 77.8, 71.8, 70.7, 65.6,
55.5, 55.3, 55.2, 42.2, 40.4, 25.9, 19.3, 18.3, 17.5, 9.6, -5.32,
-5.39; IR (neat) 2952, 2928, 2856, 1613, 1513, 1463, 1247, 1082,
837 cm-1; HRMS (FAB) calcd for (C36H56O6Si þ Na)þ
635.3738, found 635.3772; TLC Rf = 0.5, hexanes/EtOAc =
4:1; [R]rt -3.00 (c = 0.95, DCM).
Hz, 1H), 2.25 (dd, J = 7.4 and 14.0 Hz, 1H), 1.68 (d, J = 1.4 Hz,
3H), 1.62 (ddq, J = 2.2, 9.1, and 7.0 Hz, 1H), 0.97 (d, J = 7.5 Hz,
3H), 0.91 (s, 9H), 0.80 (d, J = 7.5 Hz, 3H), 0.061 (s, 3H), 0.059 (s,
3H); 13C NMR (125 MHz, CDCl3) δ 205.1, 159.1, 159.2, 138.5,
130.9, 130.9, 129.3, 129.2, 127.4, 113.8, 113.7, 78.4, 78.1, 77.7, 73.9,
71.8, 65.5, 55.28, 55.27, 55.0, 49.8, 42.2, 40.5, 25.9, 18.3, 17.4, 11.1,
9.5, -5.32, -5.39; IR (neat) 2952, 2932, 2856, 1724, 1613, 1513,
1248,1036, 837 cm-1; TLC Rf = 0.4, hexanes/EtOAc = 4:1;
[R]rt þ2.0 (c = 0.84, DCM). Anal. Calcd for C36H56O7Si: C,
68.75; H, 8.97. Found: C, 69.14; H, 8.65.
(-)-6-{[2S-(2R*,3R*,4R*,5R*,6S*,10S*),7E]-4,10-Dihydroxy-
6-methoxy-3,5,8-trimethyl-11-[[(1,1-dimethylethyl)dimethylsilyl]-
oxy]-2-[(trimethylsilyl)oxy]-undec-7-enyl}-2,2-dimethyl-4H-1,3-
dioxin-4-one (43). A flask containing 42 (235 mg, 0.384 mmol)
was brought into a drybox where solid 9-BBN dimer (235 mg,
1.91 mmol) was added. The flask was taken out of the drybox,
THF (4 mL) was added at -78 °C, and the solution was warmed
to rt. The system was stirred for 18 h before H2O2 (30%, 0.6 mL)
and aqueous NaOH (10%, 3.8 mL) were added at 0 °C. After
45 min, the reaction mixture was extracted with DCM and dried
over MgSO4. Separation by flash chromatography (hexanes/
EtOAc=7:3) gave a mixture of both diastereomers (7:1 ratio).
MPLC (hexanes/EtOAc = 7:3) separation afforded the desired
alcohol (þ)-[2R-(2R*,3R*,4R*,5R*,9R*),6E]-5-methoxy-3,9-bis-
[(4-methoxyphenyl)methoxy]-2,4,7-trimethyl-10-[[(1,1-dimethyl-
ethyl)dimethylsilyl]oxy]deca-6-en-1-ol (S31, 168 mg, 70%) and a
minor amount ofthe C2-epimer (S32), each asa colorlessoil. S31:
1H NMR (500 MHz, CDCl3) δ 7.31 (d, J = 8.8 Hz, 2H), 7.25 (d,
J =8.7 Hz, 2H), 6.90 (d, J =8.8 Hz, 2H), 6.85 (d, J=8.7 Hz, 2H),
5.01 (dq, J = 9.1 and 1.2 Hz, 1H), 4.62 (d, J = 11.3 Hz, 1H), 4.59
(d, J = 11.0 Hz, 1H), 4.56 (d, J = 11.0 Hz, 1H), 4.51 (d, J = 11.3
Hz, 1H), 3.85 (dd, J = 1.8 and 9.0 Hz, 1H), 3.81 (s, 3H), 3.80 (s,
3H), 3.75 (dd, J = 9.7 and 9.7 Hz, 1H) 3.50-3.71 (m, 5H), 3.17 (s,
3H), 2.73 (dd, J = 3.3 and 8.7 Hz, 1H), 2.33 (dd, J = 5.1 and 14.0
Hz, 1H), 2.25 (dd, J = 7.5 and 14.0 Hz, 1H), 1.92 (ddq, J = 4.0,
9.0, and 7.0 Hz, 1H), 1.65 (ddq, J = 1.4, 8.3, and 6.8 Hz, 1H), 1.68
(d, J = 1.5 Hz, 3H), 0.90 (s, 9H), 0.83 (d, J = 7.1 Hz, 3H), 0.80 (d,
J = 7.1 Hz, 3H), 0.061 (s, 3H), 0.059 (s, 3H); 13C NMR (125 MHz,
CDCl3) δ 159.2, 159.1, 138.2, 131.0, 130.9, 129.3, 129.3, 127.6,
113.9, 113.6, 81.8, 78.4, 78.2, 74.2, 71.8, 67.2, 65.5, 55.3, 55.3, 55.1,
42.2, 40.4, 38.3, 25.9, 18.3, 17.4, 14.1, 9.8, -5.33, -5.40; IR (neat)
BF3 Et2O(45 μL, 0.36 mmol) was added over 2 min to aldehyde
3
S33 (113 mg, 0.18 mmol) and ketene acetal 20 (385 mg, 1.8 mmol)
in DCM (9 mL) at -78 °C. After 45 min, the reaction mixture was
allowed to warm to room temperature before being quenched with
saturated aqueous NaHCO3. The resulting mixture was extracted
with DCM, dried over MgSO4, and concentrated. Flash chroma-
tography (hexanes/EtOAc = 7:3 to 1:1) gave (þ)-6-{[2S-(2R*,
3S*,4S*,5S*,6S*,10S*),7E]-2-hydroxy-6-methoxy-5,10-bis[(4-
methoxyphenyl)methoxy]-3,5,8-trimethyl-11-[[(1,1-dimethyl-
ethyl)dimethylsilyl]oxy]undec-7-enyl}-2,2-dimethyl-4H-1,3-dioxin-
4-one (S34, 125 mg, 90%). S34: 1H NMR (500 MHz, CDCl3) δ
7.29 (d, J = 8.4 Hz, 2H), 7.25 (d, J = 8.4 Hz, 2H), 6.90 (d, J = 8.4
Hz, 2H), 6.85 (d, J = 8.4 Hz, 2H), 5.27 (s, 1H), 5.02 (d, J = 9.6
Hz, 1H), 4.63 (d, J = 10.6 Hz, 1H), 4.61 (d, J = 10.6 Hz, 1H), 4.51
(d, J = 10.6 Hz, 1H), 4.50 (d, J = 10.6 Hz, 1H), 4.16 (m, 1H), 3.87
(dd, J = 2.4 and 8.2 Hz, 1H), 3.81 (s, 3H), 3.79 (s, 3H), 3.78 (dd,
J = 9.6 and 9.6 Hz, 1H), 3.58-3.72 (m, 3H), 3.20 (s, 3H), 2.38
(dd, J = 9.45 and 14.4 Hz, 2H), 2.35 (dd, J = 4.53 and 12.8 Hz,
1H), 2.33 (d, J = 5.8 Hz, 1H), 2.26 (dd, J = 6.8 and 12.8 Hz, 1H),
2.23 (dd, J = 4.15 and 14.4 Hz, 1H), 1.70 (m, 2H), 1.69 (s, 3H),
0.91 (s, 9H), 0.85 (d, J = 7.0 Hz, 3H), 0.81 (d, J = 7.0 Hz, 3H),
0.06 (s, 6H); 13C NMR (125 MHz, CDCl3) δ 169.9, 161.1, 159.3,
159.0, 138.3, 130.8, 130.7, 129.4, 129.3, 127.3, 113.8, 113.6, 106.4,
94.7, 79.9, 78.4, 78.1, 74.2, 71.7, 68.7, 65.4, 55.2, 55.2, 55.0, 42.1,
40.8, 40.7, 39.3, 25.9, 25.2, 24.7, 18.2, 17.4, 10.6, 9.8, -5.37,
-5.43; IR (neat) 3457, 2928, 2856, 1726, 1634, 1613, 1512, 1389,
1375 cm-1; HRMS (FAB) calcd for (C43H66O10Si þ Na)þ
793.4318, found 793.4336; TLC Rf = 0.35, hexanes/EtOAc =
1:1; [R]rt þ7.2 (c = 0.31, DCM).
3470, 2953, 2928, 2857, 1613, 1513, 1248, 1090, 1036, 837 cm-1
;
HRMS (FAB) calcd for (C36H58O7Si þ Na)þ 653.3844, found
653.3851; TLC Rf = 0.2, hexanes/EtOAc = 7:3; [R]rt þ23.2 (c =
0.45, DCM). S32: 1H NMR (500 MHz, CDCl3) δ 7.29 (d, J = 8.6
Hz, 2H), 7.25 (d, J =8.6 Hz, 2H), 6.89 (d, J =8.6 Hz, 2H), 6.85 (d,
J = 8.6 Hz, 2H), 5.01 (d, J = 9.8 Hz, 1H), 4.62 (d, J = 10.9 Hz,
1H), 4.58 (d, J = 10.4 Hz, 1H), 4.48 (d, J = 10.9 Hz, 1H), 4.51 (d,
J = 10.3 Hz, 1H), 3.80 (s, 3H), 3.79 (s, 3H), 3.78 (dd, J = 2.3 and
7.0 Hz, 1H), 3.50 - 3.70 (m, 6H), 3.12 (s, 3H), 2.31 (dd, J=5.1 and
14.2 Hz, 1H), 2.24 (dd J = 7.2 and 14.2 Hz, 1H), 1.96 (ddq, J =
6.0, 7.0, and 7.0 Hz, 1H), 1.72 (ddq, J = 2.1, 6.6, and 9.0 Hz, 1H),
1.67 (d, J=1.5 Hz, 3H), 1.01 (d, J= 7.3 Hz, 3H), 0.90 (s, 9H), 0.85
(d, J = 6.9 Hz, 3H), 0.06 (s, 6H); IR (neat) 3434, 2953, 2928, 2856,
1613, 1513, 1247, 1096, 837 cm-1; HRMS (FAB) calcd for
(C36H58O7Si þ Na)þ 653.3844, found 653.3857; TLC Rf = 0.2,
hexanes/EtOAc = 7:3; [R]rt þ6.62 (c = 0.64, DCM).
TMSCl (0.046 mL, 0.36 mmol) was added to a solution of S34
(28 mg, 0.036 mmol), Et3N (0.15 mL, 1.08 mmol), and DCM
(0.3 mL) at rt. The resulting mixture was stirred until the reaction
was deemed complete by TLC, ca. 4 h, at which time the solu-
tion had taken on a pink color. The mixture was quenched with
aqueous NaHCO3, extracted with DCM, dried over Na2SO4, and
concentrated to furnish crude silyl ether, which was carried
forward without purification. This oil was first dissolved in wet
DCM (1.2 mL) and H2O (100 μL). DDQ (65 mg, 0.29 mmol) was
added at rt, and the mixture was stirred for 0.5 h. Aqueous
NaHCO3 was added, and the mixture was stirred for 5 min,
diluted with water, and extracted with DCM. The organic layers
were dried over Na2SO4 and concentrated. Flash chromatogra-
phy (hexanes/EtOAc =7:3 to 100% EtOAc) furnished diol 43
(17 mg, 78%) as a colorless oil. 43: 1H NMR (500 MHz, CDCl3) δ
5.29 (s, 1H), 5.20 (d, J = 9.3 Hz, 1H), 4.36 (ddd, J = 2.2, 4.3, 8.6
Hz, 1H), 3.95 (dd, J = 6.7 and 9.4 Hz, 1H), 3.83 (ddd, J = 1.5,
1.5, and 9.7 Hz, 1H), 3.81 (m, 1H), 3.63 (dd, J = 3.6, 9.9 Hz, 1H),
3.46 (dd, J = 6.8 and 9.5 Hz, 1H), 3.44 (d, J = 1.8 Hz, 1H), 3.25
(s, 3H), 2.47 (dd, J = 8.8 and 13.8 Hz, 2H), 2.41 (d, J = 3.6, 1H),
2.31 (dd, J = 4.3 and 13.8 Hz, 1H), 2.21 (bs, 1H), 2.19 (bs, 1H),
1.75 (d, J = 1.4 Hz, 3H), 1.70 (s, 3H), 1.68 (s, 3H), 1.63 (m, 2H)
0.91 (s, 9H), 0.86 (d, J = 7.2 Hz, 3H), 0.74 (d, J = 6.8 Hz,
3H), 0.12 (s, 9H), 0.07 (s, 6H); 13C NMR (125 MHz, CDCl3) δ
169.6, 161.1, 137.0, 127.6, 106.4, 95.2, 80.2, 70.9, 70.9, 69.7,
66.9, 56.1, 43.6, 40.6, 39.6, 39.2, 26.2, 25.8, 24.0, 18.3, 17.0,
10.6, 8.4, 0.19, -5.38, -5.41; IR (neat) 3502, 2953, 2931, 2857,
Dess-Martin periodinane (158 mg, 0.37 mmol) was added to
alcohol S31 (158 mg, 0.25 mmol) and DCM (12 mL) at rt. The
resulting cloudy mixture was stirred 1 h before being placed
directly onto a flash column. Flash chromatography (hexanes/
EtOAc = 9:1 to 4:1) afforded (þ)-[2S-(2R*,3R*,4S*,5S*,9S*),
6E]-5-methoxy-3,9-bis-[(4-methoxyphenyl)-methoxy]-2,4,7-tri-
methyl-10-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-6-decenal (S33,
119 mg, 76%) as a colorless oil. S33: 1H NMR (500 MHz, CDCl3)
δ 9.73 (d, J = 3.0 Hz, 1H), 7.25 (d, J = 8.7 Hz, 2H), 7.24 (d, J =
8.7 Hz, 2H), 6.88 (d, J = 8.7 Hz, 2H), 6.85 (d, J = 8.7 Hz, 2H),
5.02 (d, J = 9.6 Hz, 1H), 4.62 (d, J = 11.4 Hz, 1H), 4.51 (s, 2H),
4.50 (d, J = 11.4 Hz, 1H), 4.15 (dd, J = 2.2 and 9.3 Hz, 1H), 3.80
(s, 3H), 3.79 (s, 3H), 3.82 (m, 1H), 3.57-3.70 (m, 3H), 3.17 (s, 3H),
2.67 (ddq, J = 3.0, 9.3, and 7.0 Hz, 1H), 2.33 (dd, J = 5.0 and 14.0
1734, 1635, 1464, 1390, 1375, 1273, 1251, 1085, 840 cm-1
;
HRMS (FAB) calcd for (C30H58O8Si2 þ Na)þ 625.3562, found
7058 J. Org. Chem. Vol. 75, No. 21, 2010

Hoye et al.
JOCFeatured Article
625.3570; TLC Rf = 0.6, hexanes/EtOAc = 1:1; [R]rt -22.8
(c = 0.29, DCM).
diluted with EtOAc(500 μL), quenched with aqueous NH4Cl, and
diluted with H2O (5 mL). The aqueous layer was extracted with
EtOAc (3 ꢀ 5 mL). The combined organic layers were washed
with brine (5 mL), washed with water (5 mL), dried over Na2SO4,
and concentrated. The crude product was passed through a
plug of silica gel (hexanes/EtOAc = 1:1) to afford crude aldehyde,
which was immediately carried on to the next reaction. A solution
of n-BuLi (0.3 mL, 2.05 M, 0.67 mmol) was added to neat
hexamethyldisilazane (0.14 mL, 0.67 mmol) in a round-bottom
flask at 0 °C. The solution was stirred for 0.5 h at which time a
white precipitateformed. THF (2.9mL) was then added to make a
0.2 M solution of LiHMDS. Phosphonate 433c,e (14 mg, 0.051
mmol) was placed in a vial and dissolved in THF (0.3 mL). To this
solution was added LiHMDS (255 μL, 0.2 M in THF, 0.051
mmol) at -78 °C, resulting in a dark brown color. The mixture
was stirred 3 min at -78 °C before the aldehyde from the previous
step (in THF, 200 μL) was added. The vessel was immediately
removed from the dry ice bath and allowed to warm to rt over
4 min before being quenched with aqueous NH4Cl, extracted with
EtOAc, dried over Na2SO4, and concentrated. The crude pro-
duct was passed through a pipet column of silica gel (hexanes/
EtOAc = 4:1) to affordthe TMS-protected product. The silylated
product was dissolved in THF (0.5 mL), TBAF (30 μL, 1.0 M in
THF) was added, and the resulting mixture was stirred for 5 min at
rt. The solvent was removed with a stream of N2, and the resulting
oil was loaded onto a flash column with DCM. Flash chromatog-
raphy (hexanes/EtOAc = 7:3 to 1:1) afforded 49 (3 mg, 54%): 1H
NMR (500 MHz, CDCl3) δ 6.48 (dd, J = 10.9 and 15.4 Hz, 1H),
6.27 (dd, J = 10.9 and 15.1 Hz, 1H), 5.83 (m, 1H), 5.76 (dd, J = 6.2
and 15.1 Hz, 1H), 5.57 (dd, J = 2.2 and 15.5 Hz, 1H), 5.31 (d, J =
9.7 Hz, 1H), 5.03 (d, J = 2.4 Hz, 1H), 3.80 (dd, J = 2.4 and 9.5 Hz,
1H), 3.79 (m, 1H), 3.61 (dd, J = 2.6 and 10.2 Hz, 1H), 3.24 (s, 3H),
3.18 (ddd, J = 3.2, 5.6, and 6.2 Hz, 1H), 2.55 (d, J = 12.9 Hz, 1H),
2.44 (d, J = 12.9 Hz, 1H), 2.29 (m, 2H), 2.22 (ddq, J = 2.5, 2.5, and
6.9 Hz, 1H), 2.10 (dd, J = 4.6 and 11.8 Hz, 1H), 1.78 (m, 1H), 1.74
(s, 3H), 1.39 (m, 1H) 1.30 (m, 4H), 0.98 (app d, J=6.8 Hz, 6H); 13C
NMR (125 MHz, CDCl3) δ 171.8, 140.1, 132.7, 132.3, 130.9, 127.8,
112.5, 95.3, 92.2, 79.8, 77.2, 75.0, 71.5, 69.5, 55.2, 46.9, 44.7, 43.7,
40.1, 36.8, 34.3, 19.3, 16.1, 12.06, 12.03, 6.5; IR (neat) 3452, 3364,
2953, 2923, 2853, 1700, 1465, 1457, 1225 cm-1;HRMS(FAB) calcd
for (C26H35ClO6 þ Na)þ 501.2014, found 501.2037; TLC Rf = 0.5,
hexanes/EtOAc = 1:1; [R]rt -53.8 (c = 0.5, CHCl3).
(-)-{3aR(3aR*,4S*,6R*,7R*,7aR*)}-6-[[(1S*,5R*,7E,9R*,10R*,
11R*,12R*,13S*)-5-[(1E,3E)-6-[(1S*,2R*)-2-Chlorocyclopropyl]-1,3-
hexadien-5-yn-1-yl]-1-hydroxy-9-methoxy-7,10,12-trimethyl-3-oxo-
4,15-dioxabicyclo[9.3.1]pentadec-7-en-13-yl]oxy]-7-methoxy-4,7a-
dimethyl-4H-pyrano[3,4-d]oxazol-2(3H)-one (1). To a mixture of
the aglycon 49 (2 mg, 0.004 mmol), carbohydrate 343f (3 mg,
0.008), and powdered molecular sieves (20 mg) in DCM (300 μL)
was added TMSOTf (0.055 M in DCM, 15 μL, 0.836 μmol) at
0 °C. TLC still showed starting material after stirring for 30 min,
and so additional carbohydrate 3 (1.5 mg, 0.004 mmol) was added.
After the addition, TLC showed an absence of starting material
within 10 min. The mixture was quenched with saturated aqueous
NaHCO3. The resulting solution was diluted with H2O, extracted
with DCM, dried over Na2SO4, and purified by HPLC (100%
EtOAc) to afford (-)-callipeltoside A (1) (2 mg, 70%): 1H NMR
(500 MHz, CD3OD) δ 6.49 (dd, J = 10.8 and 15.4 Hz, 1H), 6.33
(dd, J =10.8 and 14.1 Hz, 1H), 5.83 (m, 1H), 5.80 (m, 1H), 5.64
(dd, J = 1.9 and 15.4 Hz, 1H), 5.26 (d, J = 9.7 Hz, 1H), 4.71 (d,
J = 6.2 Hz, 1H), 3.95 (dd, J = 1.9 and 6.5 Hz, 1H), 3.87 (dd, J =
2.4 and 9.5 Hz, 1H), 3.72 (dd, J = 4.7, 10.7, and 10.7 Hz, 1H), 3.64
(dd, J = 2.4 and 10.4 Hz, 1H), 3.59 (s, 3H), 3.44 (d, J = 1.9 Hz,
1H), 3.42 (d, J = 6.1 Hz, 1H), 3.24 (m), 3.21 (s, 3H), 2.52 (d, J =
12.8 Hz, 1H), 2.46 (d, J = 12.8 Hz), 2.33 (bd, J = 13.3 Hz, 1H),
2.26 (dd, J = 11.1 and 13.3 Hz, 1H), 2.21 (m, 1H), 2.21 (ddq, 2.3,
2.3, and 7.2 Hz, 1H), 1.80 (m, 1H), 1.74 (s, 3H), 1.50 (s, 3H), 1.50
(ddq, J = 3.9, 10.3, and 6.6 Hz, 1H), 1.39 (dd, J = 11.1 and
(-)-[1S*(1R*,5S*,9S*,10S*,11R*,12R*,13R*)7E)-1-Hydroxy-
9-methoxy-7,10,12-trimethyl-5-[[[(1,1-dimethylethyl)dimethylsilyl]-
oxy]methyl]-13-[(trimethylsilyl)oxy]-4,15-dioxabicyclo[9.3.1]-
pentadec-7-en-3-one (44). Benzene (200 mL) was placed in a
round-bottom flask equipped with a Dean-Stark trap. The flask
was heated, and 40 mL of benzene was removed through the trap.
The condenser was removed, and diol 43 (16 mg, 0.027 mmol) in
benzene (2 mL) was transferred into the flask. The condenser was
replaced, and the mixture was refluxed for 12 h. The reaction
mixture was cooled to rt, concentrated, and purified by flash
chromatography (hexanes/EtOAc = 9:1) to afford macrolactone
44 (11 mg, 78%): 1H NMR (500 MHz, CDCl3) δ 5.37 (dddd, J =
11.6, 6.8, 4.4, 2.5 Hz, 1H), 5.28 (dq, J = 9.5, 1.2 Hz, 1H), 5.07 (d,
J = 2.5 Hz, 1H), 3.80 (dd, J = 9.3, 2.4 Hz, 1H), 3.77 (m, 1H), 3.70
(dd, J = 11.0, 6.7 Hz, 1H), 3.66 (dd, J = 11.1, 4.5 Hz, 1H), 3.61
(dd, J = 10.4, 2.7 Hz, 1H), 3.24 (s, 3H), 2.50 (d, J = 12.8 Hz, 1H),
2.40 (d, J = 12.8 Hz, 1H), 2.24 (dd, J = 13.4, 2.6 Hz, 1H), 2.20
(ddq, J = 2.4, 2.4, 7.0 Hz, 2H), 2.16 (dd, J =13.4, 11.7 Hz, 1H),
1.97 (dd, J = 12.0, 4.7 Hz, 1H), 1.72 (s, 3H), 1.42 (ddq, J = 10.2,
10.2, 6.1 Hz, 1H), 1.35 (ddd, J = 11.9, 10.7, 2.4 Hz, 1H), 0.97 (d,
J = 7.1 Hz, 3H), 0.89 (d, J = 6.7 Hz, 3H), 0.88 (s, 9H), 0.13 (s,
9H), 0.05 (s, 3H), 0.05 (s, 3H); 13C NMR (125 MHz, CDCl3) δ
172.4, 132.6, 127.3, 95.4, 79.9, 72.7, 70.1, 65.17, 65.12, 55.2, 44.6,
44.4, 42.6, 40.1, 37.1, 25.7, 18.2, 16.1, 12.3, 6.6, -0.02, -5.30,
-5.33; IR (neat) 3451, 2956, 2929, 2859, 1706, 1251, 1075, 838
cm-1; HRMS (FAB) calcd for (C27H52O7Si2 þ Na)þ 567.3144,
found 567.3159; TLC Rf = 0.4, hexanes/EtOAc = 9:1; [R]rt -19.8
(c = 0.93, DCM).
(-)-[1S*(1R*,5S*,9S*,10S*,11R*,12R*,13R*)7E]-1-Hydroxy-
5-(hydroxymethyl)-9-methoxy-7,10,12-trimethyl-13-[(trimethyl-
silyl)oxy]-4,15-dioxabicyclo[9.3.1]pentadec-7-en-3-one (48). TBAF
(0.28 mL, 1.0 M in THF, 0.28 mmol) wasadded to44 (11 mg, 0.020
mmol) in THF (0.5 mL) at rt and stirred for 10 min. The solution
was placed on a pipet column and purified by flash chromatogra-
phy (100% EtOAc) to afford a diol that was immediately carried
into the next reaction. TMSCl (0.05 mL, 0.40 mmol) was added
to a mixture of the diol, NEt3 (0.17 mL, 1.21 mmol), and DCM
(0.2 mL) at rt. The mixture was stirred for 2 h, quenched with
aqueous NaHCO3, diluted with water, extracted with DCM, dried
over Na2SO4, and concentrated to give a crude oil. This lactone
was dissolved in MeOH (1 mL), NaHCO3 (5 mg) was added, and
the resulting mixture was stirred for 2 h. The mixture was diluted
with water, extracted with DCM, dried over Na2SO4, and concen-
trated. Purification by flash chromatography (hexanes/EtOAc =
1
19:1) afforded 48 (6 mg, 70% over three steps): H NMR (500
MHz, CDCl3) δ 5.42 (dddd, J = 2.4, 3.7, 6.2, and 8.7 Hz, 1H), 5.31
(d, J = 9.4 Hz, 1H), 5.00 (d, J = 2.4 Hz, 1H), 3.8 (dd, J = 2.2 and
9.6 Hz, 1H), 3.76 (m, 3H), 3.61 (dd, J = 2.5, 10.3 Hz, 1H), 3.24 (s,
3H), 2.54 (d, J = 13.0 Hz, 1H), 2.44 (d, J = 13.0 Hz, 1H), 2.30 (dd,
J = 12.0 and 12.0 Hz, 1H), 2.21 (m, 2H), 1.98 (dd, J= 4.6 and 12.0
Hz, 1H), 1.74 (s, 3H), 1.61 (dd, J = 5.9 and 5.9 Hz, 1H), 1.43 (ddq,
J = 10.3, 10.3, and 6.5 Hz, 1H), 1.36 (ddd, J = 2.4, 10.7, and 12.0
Hz, 1H), 0.97 (d, J = 7.3 Hz, 3H), 0.90 (d, J = 6.4 Hz, 3H), 0.14 (s,
9H); 13CNMR(125MHz, CDCl3) δ172.4, 132.2, 127.7, 99.4, 79.8,
75.1, 72.8, 70.0, 64.9, 55.2, 44.7, 44.3, 42.4, 40.1, 37.0, 16.2, 12.4,
6.6, 0.30; IR (neat) 3434, 2962, 2930, 2874, 1704, 1251, 1227, 1182,
1075, 891, 841 cm-1; HRMS (FAB) calcd for (C21H38O7Si þ Na)þ
453.2279, found 453.2291; TLC Rf = 0.5, hexanes/EtOAc = 1:1;
[R]rt -23.9 (c = 0.33, DCM).
(-)-[1S(1R*,5S*,9S*,10S*,11S*,12S*,13R*)7E)-5-[(1E,3E )-
6-((1R*,2S*)-2-Chlorocyclopropyl)-1,3-hexadien-5-yn-1-yl]-1,13-
dihydroxy-9-methoxy-7,10,12-trimethyl-4,15-dioxabicyclo[9.3.1]-
pentadec-7-en-3-one (49)2,3a,3c-3e. Sulfur trioxide pyridine(19mg,
3
0.12 mmol) was added to a mixture of alcohol 48 (5 mg, 0.01
mmol), TEA (24.0 μL, 0.174 mmol), DCM (100 μL), and DMSO
(300 μL) at 0 °C. The mixture was stirred 0.5 h at which time it was
J. Org. Chem. Vol. 75, No. 21, 2010 7059

Hoye et al.
JOCFeatured Article
12.2 Hz, 1H), 1.27 (m, 2H), 1.08 (d, J = 6.5 Hz, 3H), 0.99 (d, J =
6.5 Hz, 3H), 0.95 (d, J = 7.0 Hz, 3H); 13C NMR* (125 MHz,
CD3OD) δ 172.9, 141.6, 134.4, 134.3, 132.0, 128.4, 113.5, 103.6,
96.6, 92.8, 83.9, 83.0, 81.4, 78.7, 78.4, 76.4, 72.7, 65.3, 62.7, 62.0,
55.4, 47.8, 46.1, 44.5, 36.8, 39.9, 38.2, 35.9, 35.1, 30.8, 23.0, 19.8,
16.3, 15.9, 12.7, 6.8; *the weak carbamate carbonyl resonance at δ
161.1 ppm reported for the natural sample of callipeltoside A was
not observed; IR (neat) 3452, 3266, 2921, 2852, 1750, 1699, 1464,
1358, 988 cm-1; HRMS (FAB) calcd for (C35H48ClNO10 þ Na)þ
700.2864, found 700.2883; TLC Rf = 0.5, hexanes/EtOAc = 1:1;
[R]rt -53.8 (c = 0.5, CHCl3).
Acknowledgment. These studies were supported by the
National Cancer Institute (CA-76497) of the United States
National Institutes of Health. We thank Mr. Aaron M.
Johnson for his preparation of intermediates enroute to
fragments 3 and 4.
Supporting Information Available: Experimental proce-
1
dures, characterization data, and copies of H and 13C NMR
spectra for new compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
7060 J. Org. Chem. Vol. 75, No. 21, 2010