Chemical synthesis and biological evaluation of novel epothilone B and trans-12,13-cyclopropyl epothilone B analogues

Article abstract of DOI:10.1016/S0040-4020(02)00655-5

In addition to the total synthesis of the thiomethyl thiazole side chain analogue of epothilone B (3), a series of related trans-12,13-cyclopropyl epothilone B analogues (6, 8, 10, 12-14) was accomplished. While the synthesis of the epothilone B analogue (3) proceeded through a Stille coupling of a vinyl iodide substrate containing the epothilone macrocycle with the appropriate side chain stannane, that of the cyclopropyl analogues (6, 8, 10, 12-14) involved a convergent strategy in which a Nozaki-Hiyama-Kishi coupling as a means of introducing the side chains prior to Yamaguchi macrolactonization and final elaboration to the target molecules. The synthesized analogues were subjected to biological evaluation involving in vitro tubulin polymerization, affinity for the microtubule Taxol binding site and cell cytotoxicity assays. The results identified the methylthio thiazole side chain as a potency enhancing moiety for the epothilones and shed further light on the structure-activity relationships within this important class of chemotherapeutic agents.

Full text of DOI:10.1016/S0040-4020(02)00655-5

Tetrahedron 58 (2002) 6413–6432
Chemical synthesis and biological evaluation of novel epothilone B
and trans-12,13-cyclopropyl epothilone B analogues
c
c
K. C. Nicolaou,a,b Andreas Ritzen,a,b Kenji Namoto,a,b Ruben M. Buey, J. Fernando Dıaz,
,
*
´
´
´
c
d
e
f
´
Jose M. Andreu, Markus Wartmann, Karl-Heinz Altmann, Aurora O’Brate
and Paraskevi Giannakakouf
aDepartment of Chemistry and Skaggs Institute for Chemical Biology, Scripps Research Institute, 10550 North Torrey Pines Road,
La Jolla, CA 92037, USA
bDepartment of Chemistry and Biochemistry, University of California–San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
cCentro de Investigaciones Biologicas, CSIC, Velazquez 144, 20006 Madrid, Spain
dNovartis Pharma AG, Oncology Business Unit, CH-4002, Basel, Switzerland
eNovartis Pharma AG, Corporate Research, CH-4002, Basel, Switzerland
fWinship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA
Received 27 March 2002; accepted 25 May 2002
Abstract—In addition to the total synthesis of the thiomethyl thiazole side chain analogue of epothilone B (3), a series of related trans-12,13-
cyclopropyl epothilone B analogues (6, 8, 10, 12–14) was accomplished. While the synthesis of the epothilone B analogue (3) proceeded
through a Stille coupling of a vinyl iodide substrate containing the epothilone macrocycle with the appropriate side chain stannane, that of the
cyclopropyl analogues (6, 8, 10, 12–14) involved a convergent strategy in which a Nozaki–Hiyama–Kishi coupling as a means of
introducing the side chains prior to Yamaguchi macrolactonization and final elaboration to the target molecules. The synthesized analogues
were subjected to biological evaluation involving in vitro tubulin polymerization, affinity for the microtubule Taxolw binding site and cell
cytotoxicity assays. The results identified the methylthio thiazole side chain as a potency enhancing moiety for the epothilones and shed
further light on the structure–activity relationships within this important class of chemotherapeutic agents. q 2002 Elsevier Science Ltd. All
rights reserved.
1. Introduction
potent analogues (i.e. compounds 3, 6, 8–14, Fig. 1) active
against a variety of cell lines, including Taxolw-resistant
tumor cells. It is worth noting at the outset that these
biological studies were made possible only through the
power of chemical synthesis which served well to deliver
them expeditiously, as will now be described.
The excitement generated by the structural elucidation and
biological activity of epothilones (e.g. 1 and 2, Fig. 1)
continues to drive multifaceted studies in chemistry, biology
and medicine.1 Advancing clinical trials with a number of
drug candidates as anticancer agents add further urgency to
continuing research programs in the field. We have recently
reported the design, chemical synthesis, and biological
evaluation of a number of 12,13-cyclopropyl epothilone
analogues.2,3 Particularly interesting was the potency of the
trans-12,13-cyclopropyl set of epothilones A carrying the
methylthiazole or pyridine side chains (structures 5 and 7,
Fig. 1).3 This striking observation coupled with our earlier
finding of the enhanced potency of thiomethyl thiazole
analogues4 of epothilones C and D prompted us to embark
on the synthesis and biological investigation of a new
epothilone B series in anticipation of improved biological
profiles. In this article we report our most recent studies in
the epothilone field culminating in a number of highly
2. Results and discussion
2.1. Design and chemical synthesis of epothilone
analogues
As an initial foray, we decided to confirm the potency
enhancement bestowed on the epothilone scaffold by the
methylthio group 4 as compared to the methyl substituent in
the epothilone B series. The methylthiothiazole epothilone
B (3) was thus synthesized by Stille coupling of stannane
165 with vinyl iodide 156 (72% yield) as shown in Scheme
1. The observed high potency of analogue 3 against a series
of tumor cell lines (see Table 1) encouraged us to proceed
with the design and synthesis of an entire family of
methylthio analogues as well as a number of new pyridine-
containing epothilones.
Keywords: epothilones; antitumor agents; chemical synthesis; structure–
activity relationships.
*
Corresponding author. Tel.: þ1-858-784-2400; fax: þ1-858-784-2469;
e-mail: kcn@scripps.edu
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00655-5

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K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
Figure 1. Structures of selected natural and designed epothilones. Grey boxes indicate compounds synthesized in this study.
Scheme 2 outlines, in retrosynthetic format, the pathway
that was followed for the construction of the designed
epothilone B analogues. Based on our previously reported
strategy, the adopted sequence required a Charette cyclo-
propanation reaction3,7 to establish early on in the synthesis
the 12,13-cyclopropyl site, an aldol reaction according to
our optimized procedure6 to construct the C6–C7 bond with
its two stereocenters, a Nozaki–Hiyama–Kishi coupling3,8
to introduce the side chain, and a Yamaguchi macro-
lactonizaion9 to complete the macrocyclic structure. Key
building blocks 18–20 were thus defined as the starting
points for these constructions. Construction of the corre-
sponding epothilone A analogues was envisaged to be
carried out in the same manner as previously reported by
us.3
(O3; NaBH4) of the remaining double bond led to compound
23 in 89% overall yield. Conversion of alcohol 23 to the
corresponding iodide (24, 95% yield) was accomplished
upon mesylation and subsequent reaction with NaI.
Alkylation of (2)-propionaldehyde SAMP hydrazone
(25)9c,10 with iodide 24 under the influence of LDA gave
compound 26 (84% yield), whose cleavage (MeI; HClaq) led
to aldehyde 17 in 86% yield. The ratio of the resulting C-8
epimers was determined to be ca. 97:3 by 1H NMR analysis
of the MTPA esters derived from aldehyde 17.11 The aldol
condensation between ketone 19 and aldehyde 17 under the
previously defined conditions (LDA (2.4 equiv.), ketone 19
(2.3 equiv.), 278 to 2408C, 30 min; then aldehyde 17,
2788C, 5 min)6 afforded aldol product 27 which was
isolated in a diastereomerically pure form (81% yield).
Subsequent protection of the secondary alcohol in 27 as a
TBS ether (TBSOTf, 2,6-lutidine) followed by selective
cleavage of the primary TBS group (HF·py) afforded, in
88% overall yield, alcohol 28. The latter compound was
stepwise oxidized to the carboxylic acid (DMP; then
NaClO2) which was then protected as the TMSE ester 29
(TMSE-OH, EDC, 4-DMAP) in 74% overall yield. Hydro-
genolysis of the benzyl ether in 29 followed by oxidation
Scheme 3 outlines the synthesis of the required aldehyde 32
from the readily available geraniol (18). Thus, Charette
cyclopropanation of 18 (Et2Zn–CH2I2, in the presence of
chiral ligand 21)7 furnished cyclopropyl alcohol 22 in 87%
yield and 93% ee. Protection of the hydroxy group in 22
(NaH–BnBr) (for abbreviations of reagents and protecting
groups, see legends in schemes) followed by ozonolysis
Scheme 1. Synthesis of 2-(thiomethyl)thiazole epothilone B (3) via Stille coupling. Reagents and conditions: 16 (2.0 equiv.), Pd2(dba)3·CHCl3 (0.2 equiv.),
CuI (2.0 equiv.), AsPh3 (0.8 equiv.), DMF, 258C, 72%. dba, dibenzylideneacetone.

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6415
Table 1. Cytotoxicity of epothilones 1–14 and paclitaxel against 1A9 human ovarian carcinoma cells and b-tubulin mutant cell lines selected with paclitaxel or
epothilone A
Compound
Cell line
PTX10 (b270)
IC50
1A9 IC50
A8 (b274)
PTX22 (b364)
IC50
IC50
RR
RR
RR
Epothilone A (EpoA) 1
Epothilone B (EpoB) 2
Paclitaxel (Taxolw)
tmt-EpoB 3
cis-CP-py-EpoA 4
trans-CP-EpoA 5
trans-CP-EpoB 6
trans-CP-py-EpoA 7
trans-CP-py-EpoB 8
trans-CP-pyOH-EpoA 9
trans-CP-pyOH-EpoB 10
trans-CP-tmt-EpoA 11
trans-CP-tmt-EpoB 12
trans-CP-5tmpy-EpoB 13
trans-CP-6tmpy-EpoB 14
3.1^0.72
0.3^0.05
1.3^0.22
0.17^0.08
2.4^0.99
10.1^6.59
15
0.6^0.22
1.7^0.76
0.7^0.16
1.7^1.12
1.2^0.67
3.5^1.64
14.2^5.73
114
77.3^9.25
6.5^1.70
11.3^0.83
1.3^0.65
41.6^8.58
33.9^5.56
.150
10.1^2.07
27.9^6.73
13.0^2.17
13.2^5.02
11.2^2.30
28.9^8.01
94^5
24.9
21.7
8.7
7.6
17.3
3.4
.10
16.8
16.4
18.6
7.8
9.3
8.3
6.6
.1.3
29.1^7.24
3.7^1.83
47.7^5.01
0.26^0.11
19.2^9.39
17.2^5.97
52
5.9^1.96
10.9^3.52
6.1^1.90
10.2^3.75
3.2^1.13
5.7^1.96
72.0^10.41
.150
9.4
12.3
36.7
1.5
8
1.7
3.5
9.8
6.4
8.7
6
10.1^2.10
2.1^1.45
29.4^3.69
0.25^0.17
4.2^2.18
4.7^1.68
5
1.4^0.51
5.6^3.24
1.1^0.38
2.5^1.41
0.8^0.38
11.5^3.86
20.6^9.06
104
3.3
7
22.6
1.5
1.8
0.5
0.3
2.3
3.3
1.6
1.5
0.7
3.3
1.5
0.9
2.7
1.6
5.1
.1.3
.150
The anti-proliferative effects of the tested compounds against the parental 1A9 and the paclitaxel- and epothilone-selected drug-resistant clones (PTX10,
PTX22 and A8, respectively) were assessed in a 72 h growth inhibition assay using the SRB (sulforhodamine-B) assay.17 IC50 values for each compound are
given in nM and represent the mean of 3–9 independent experiments^standard error of the mean. Relative resistance (RR) is calculated as an IC50 value for
each resistant sub-line divided by that for the parental cell line (1A9). CP, cyclopropyl; py, 5-methylpyridine side chain; pyOH, 5-hydroxymethylpyridine side
chain; 5tmpy, 5-thiomethylpyridine side chain; 6tmpy, 6-thiomethylpyridine side chain; tmt, 2-thiomethyl thiazole side chain.
with DMP led to aldehyde 30 (84% yield) whose
homologation (NaHMDS–MeOCH2PPh3Cl; then PPTS)
to the coveted higher aldehyde 32 proceeded smoothly,
and via vinyl ether 31 (ca. 1:1 E:Z ratio), with 68% overall
yield.
with propyne (Pd(PPh3)2Cl2–CuI, 96%) led to acetylenic
compound 35 which served as a precursor to vinyl iodide
20c (n-BuLi; then (n-Bu3Sn)2, CuCN, MeOH; then I2, 80%
yield). Exchange of the trityl for a MOM group within 35
(HCl(g), CHCl3; then NaH, MOM-Cl, 34% overall yield)14
allowed access to vinyl iodide 20d (67% yield) by exposure
of the resulting intermediate 36 to the same conditions
described above for the 35 to 20c conversion. Similar
chemistry was employed to construct vinyl iodides 20e–g
from 37 to 39, respectively, as shown in Scheme 4.
The side chains (20a–g, Scheme 4) were synthesized either
as previously reported (20a and b)3 or from the correspond-
ing aryl halides (33,12 37–39) as shown in Scheme 4.
Protection of 4-hydroxymethyl-2-pyridyl bromide 33 as
a trityl ether (TrCl, 4-DMAP, 100%) followed by
Sonogashira coupling13 of the resulting aryl bromide 34
Two crucial bond formations and two accompanying
deprotections separated key building blocks 32 (prepared
in this study for epothilone B analogues), 40 (prepared as
previously described for epothilone A analogues),3 and
20a–g (for side chains) from the targeted epothilone
analogues. The first operation was the Nozaki–Hiyama–
Kishi coupling8 of aldehydes 32 and 40 with vinyl iodides
20a–g. This carbon–carbon bond forming reaction worked
admirably in this instance (CrCl2, NiCl2, 4-t-BuPy, DMSO),
furnishing, after TBAF-induced carboxylic acid generation,
coupling products (41a,b,d–g, 42c and e) in yields
indicated in Scheme 5 (as ca. 1:1 mixtures of C-15
diastereomers). Each mixture of hydroxy acid diastereomers
(41a,b,d–g, 42c and e) was then subjected to Yamaguchi
macrocyclization (2,4,6-trichlorobenzoyl chloride,
4-DMAP) to afford the desired 15(S ) lactone in the
indicated (unoptimized) yields together with its 15(R)
epimer. The separation of the two epimers at this juncture
was facilitated by their rather drastically different Rf values
on silica gel. Final deprotection of protected derivatives
either with 20% TFA in CH2Cl2 (43a,b,e–g, 44c and e) or
˚
with TMSBr–4 A MS in CH2Cl2, followed by 20% TFA in
CH2Cl2 (43d), led to epothilones 6, 8–14 in the indicated
(unoptimized) yields (Scheme 5). Chromatographically and
spectroscopically pure compounds were subjected to
biological evaluations as described below.
Scheme 2. Retrosynthetic analysis of trans-cyclopropyl epothilone B
analogues (I¼6, 8, 10, 12–14).

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K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
Scheme 3. Construction of aldehyde 32. Reagents and conditions: (a) See Refs. 2 and 7; (b) NaH (1.5 equiv.), BnBr (1.5 equiv.), DMF, 0! 258C, 12 h; (c) O3,
CH2Cl2/MeOH 4:1, 2788C, 21 min; then NaBH4 (3.0 equiv.), 278!258C, 1 h, 89% for two steps; (d) MsCl (1.3 equiv.), Et3N (1.5 equiv.), CH2Cl2, 258C,
1 h; (e) NaI (3.0 equiv.), acetone, reflux, 40 min, 95% for two steps; (f) LDA (1.4 equiv.), 25 (1.3 equiv.), THF, 08C, 6 h; then 24, 298! 2108C, 14 h, 84%;
(g) MeI, 608C, 3 h; (h) 3N HCl:pentane 1:1, 258C, 3 h, 88% for two steps; (i) LDA (2.4 equiv.), 19 (2.3 equiv.), THF, 2788C, 1 h; then 2408C, 0.5 h; then 17 at
2788C, 5 min, 81%; (j) TBSOTf (2.0 equiv.), 2,6-lutidine (3.0 equiv.), CH2Cl2, 2208C, 1 h; (k) HF·py, pyridine, THF, 258C, 4 h, 88% for two steps; (l) DMP
(2.5 equiv.), NaHCO3 (2.5 equiv.), H2O, CH2Cl2, 258C, 1 h; (m) NaClO2 (3.1 equiv.), NaH2PO4 (2.1 equiv.), 2-methyl-2-butene (74 equiv.), t-BuOH, THF,
H2O, 258C, 1 h; (n) 2-(trimethylsilyl)ethanol (4.0 equiv.), EDC (1.5 equiv.), 4-DMAP (0.1 equiv.), DMF, 258C, 14 h, 74% for three steps; (o) 20% Pd(OH)2/C,
H2 (1 atm), EtOH/EtOAc 1:1, 258C, 1 h; (p) DMP (2.5 equiv.), NaHCO3 (2.5 equiv.), H2O, CH2Cl2, 258C, 1 h, 84% for two steps; (q) MeOCH2PPh3Cl
(3.0 equiv.), NaHMDS (2.8 equiv.), THF, 240! 2108C, 2 h, 84%; (r) PPTS (8.0 equiv.), dioxane:H2O 9:1, 708C, 6 h, 82%. 4-DMAP, 4-(dimethyl-
amino)pyridine; DME, 1,2-dimethoxyethane; DMP, Dess–Martin periodinane; EDC, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; HF·py,
hydrogen fluoride–pyridine complex; NaHMDS, sodium hexamethyldisilazide; PPTS, pyridinium para-toluenesulfonate; TMSE, 2-trimethylsilylethyl.
2.2. Chemical biology
tubulin polymerization assays were carried out using a set of
human epidermoid cancer cell lines, including a parent cell
line (KB-31) and a paclitaxel-resistant (due to Pgp over-
expression) cell line (KB-8511). The results of these studies
are summarized in Table 2.18,19
The biological activities of the synthesized epothilones were
evaluated through cytotoxicity, in vitro tubulin polymeri-
zation, and tubulin binding assays. Cytotoxicity was first
evaluated in a set of ovarian carcinoma cell lines, including
a parental cell line (lA9) and three drug-resistant cell lines,
namely the paclitaxel-resistant strains15 lA9/PTX10 and
lA9/PTX22 and the epothilone-resistant strain16 1A9/A8.
These resistant cell lines harbor distinct acquired b-tubulin
mutations which affect drug–tubulin interaction and result
in impaired taxane and epothilone-driven tubulin poly-
merization. The results of these biological investigations are
summarized in Table 1.17 Further cytotoxicity and in vitro
In general, there is good agreement between the in vitro
tubulin polymerization potency and the cytotoxicity profile
of the tested compounds against both the 1A9 human
ovarian carcinoma cells and the KB-31 human epidermoid
carcinoma cells. In agreement with original observations
with the naturally occuring epothilones A and B, none of the
epothilone A or B analogues tested herein appears to be a
good substrate for the drug-efflux pump P-glycoprotein

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6417
Scheme 4. Construction of vinyl iodides 20c–g. Reagents and conditions:
(a) TrCl (1.4 equiv.), 4-DMAP (1.7 equiv.), DMF, 808C, 48 h, 100%;
(b) Pd(PPh3)2Cl2 (0.01 equiv.), CuI (0.02 equiv.), HCuCCH3 (1 atm),
DMF, i-Pr2NEt, 258C, 3 h, 35: 96%; (c) (i) n-BuLi (4.0 equiv.), (n-Bu3Sn)2
(4.0 equiv.), CuCN (2.0 equiv.), MeOH, THF, 2108C, 12 h; (ii) I2
(1.05 equiv.), CH2Cl2, 08C, 5 min, 20c: 80% from 35; 20d: 67% from 36;
20e: 37% from 37; 20f: 97% from 38; 20g: 58% from 39; (d) (i) HCl(g),
CHCl3, 08C, 1 h, 69%; (ii) MOMCl (1.2 equiv.), NaH (1.2 equiv.), THF,
08C, 1 h, 50%. TrCl, triphenylmethyl chloride; 4-DMAP, 4-(dimethyl-
amino)pyridine; MOMCl, chloromethyl methyl ether.
(Pgp). This is evident by the lack of cross-resistance of each
of these analogues to the Pgp expressing cell line KB-8511,
in contrast to paclitaxel—a known Pgp substrate—which is
214-fold less active against KB-8511 cells (see Table 2). It
is noteworthy that all the epothilone analogues appear more
active against the b-tubulin mutants compared to epothilone
A (1) and epothilone B (2) (see Table 1, RR values). This is
more pronounced with compounds 10–14 for which
the relative resistance values (RR) range from 1.6 to 7.8
against PTX10 (b270) and A8 (b274) cells compared with
9.4–24.9 RR values for EpoA (1) and EpoB (2).
Furthermore, in the current study, and in agreement with
previous reports,2,15,16 we found that the paclitaxel-selected
mutant PTX22 (b364) retains almost full sensitivity to the
epothilones, and to all epothilone analogues tested in this
report (RR values #3.3).
Scheme 5. Synthesis of epothilone analogues 8–14. Reagents and
conditions: (a) CrCl2 (10 equiv.), NiCl2 (0.2 equiv.), 4-t-butylpyridine
(30 equiv.), 20 (3.0 equiv.), DMSO, 258C, overnight; (b) TBAF
(4.0 equiv.), THF, 08C, 1 h; then 258C, 1 h; (c) Et3N (6.0 equiv.), 2,4,6-
trichlorobenzoylchloride (2.4 equiv.), 41 or 42, THF, 08C, 1 h; then
4-DMAP (2.2 equiv.), toluene, 758C, 3 h; (d) 20% v/v TFA in CH2Cl2,
258C, 3 h (except 43d); (e) Estimated by 1H NMR; (f) Deprotection of 43d:
˚
TMSBr (10 equiv.), 4 A MS, CH2Cl2, 2308C, 1 h; then 20% v/v TFA in
CH2Cl2, 258C, 3 h. TBAF, tetrabutylammonium fluoride; 4-DMAP,
4-(dimethylamino)pyridine; TFA, trifluoroacetic acid; TMSBr, trimethyl-
silyl bromide; MS, molecular sieves.
fluorescent taxoid displacement assay.20 The purpose of
these experiments was to compare the equilibrium constants
with which microtubules bind at their taxane site the
epothilone analogues investigated. The inhibition of
the binding of the well-characterized fluorescent taxoid
Flutax-221–23 to microtubules by each of the epothilone
analogues was measured at 378C (Fig. 2). The resulting
In addition to the above biological assays, the relative
potency of each epothilone analogue was measured by the

6418
K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
Table 2. Tubulin polymerization potency and cytotoxicity of epothilones
1–8, 10–14, and paclitaxel against human epidermoid cancer cell lines
Table 3. Binding affinities of epothilone analogues to the taxoid binding
site of microtubules
Compound
%TPa
KB-31b
KB-8511b
RR
Compound
Kd (378C)a
DG0app (378C)b
Epothilone A (EpoA) 1
Epothilone B (EpoB) 2
Paclitaxel (Taxolw)
tmt-EpoB 3
Cis-CP-py-EpoA 4
trans-CP-EpoA 5
trans-CP-EpoB 6
trans-CP-py-EpoA 7
trans-CP-py-EpoB 8
trans-CP-pyOH-EpoB 10
trans-CP-tmt-EpoA 11
trans-CP-tmt-EpoB 12
trans-CP-5tmpy-EpoB 13
trans-CP-6tmpy-EpoB 14
78
93
52
2.15c
0.19c
2.92c
0.11
0.62c
0.97c
1.84
0.84c
0.90
0.44
0.66
0.67
6.88
109
1.91c
0.18c
626c
0.07
0.45c
0.64
1.09
0.68c
0.61
0.55
0.32
0.45
5.28
74
0.88c
0.95c
214c
0.61
0.72c
0.66c
0.59
0.81c
0.68
1.25
0.48
0.67
0.77
0.68
Epothilone A (EpoA) 1
Epothilone B (EpoB) 2
Paclitaxel (Taxolw)
tmt-EpoB 3
cis-CP-py-EpoA 4
trans-CP-EpoA 5
trans-CP-EpoB 6
trans-CP-py-EpoA 7
trans-CP-py-EpoB 8
trans-CP-pyOH-EpoB 10
trans-CP-tmt-EpoA 11
trans-CP-tmt-EpoB 12
trans-CP-5tmpy-EpoB 13
trans-CP-6tmpy-EpoB 14
34^4
1.6^0.1
93^26
244.5^0.3
252.6^0.5
242.2^0.2
254.5^1.2
249.4^0.3
248.6^0.1
248.0^0.1
251.5^0.2
251.8^0.8
248.9^0.3
252.2^0.9
251.8^0.3
251.6^0.5
243.1^0.5
99
0.64^0.24
5.2^0.8
6.5^0.1
8.0^1.8
2.1^0.4
1.9^0.6
6.0^0.6
1.6^0.5
1.8^0.2
1.9^0.3
53^8
100c
100c
82
94c
89
87
93
91
88
58
a
The extent of porcine tubulin polymerization (TP) by 4 mM compound
was quantified relative to the effect of 25 mM epothilone B (which was
defined as 100%) as described.18
Drug concentration required for maximal inhibition of cell growth (IC50
values given in nM) was assessed after a 96 h drug exposure by
quantification of cell mass using a protein dye method as described.19
KB-31: epidermoid Taxolw-sensitive cells, KB-8511: epidermoid
Taxolw-resistant cells (due to Pgp overexpression). Relative resistance
(RR) was calculated by dividing the IC50 value for the resistant cell line
by that of the sensitive cell line.
Data from Ref. 3 (%TP values for Taxolw, EpoA and EpoB were 49, 69
and 90, respectively). CP, cyclopropyl; py, 5-methylpyridine side chain;
pyOH, 5-hydroxymethylpyridine side chain; 5tmpy, 5-thiomethylpyr-
idine side chain; 6tmpy, 6-thiomethylpyridine side chain; tmt, 2-
thiomethyl thiazole side chain.
The binding of the different ligands to the taxoid site of microtubules was
measured by the displacement of a fluorescent Taxolw derivative (Flutax-
2)22 from its binding site (Fig. 2). The Flutax-2 displacement isotherm of
each ligand was measured at least twice with a fluorescence polarization
microplate reader in a modified procedure from the previous report.20
Cross-linked stabilized microtubules which had been stored under liquid
nitrogen were employed. The binding constant of the reference ligand
Flutax-2 was measured by centrifugation and fluorescence anisotropy,22 at
each temperature. The resulting reference value was 2.2£107 M21 at 378C.
b
a
The equilibrium dissociation constants (Kd) are given in nM.
The standard binding free energy changes (DG0app) are given in kJ mol21
.
c
b
compound 13, the binding affinities of the analogues tested
mirror their respective activities in both cell growth
inhibition and in vitro tubulin polymerization assays.
equilibrium dissociation constants shown in Table 3
indicate that epothilone A (1) has the lowest binding affinity
among the epothilone analogues tested (Kd¼34^4). The
most powerful ligand among those measured in this assay is
compound 3, with a Kd value of 0.64^0.24 nM, followed
by compounds 8, 11–13, with similar Kd values comprised
between 1.6 and 1.9 nM. With the possible exception of
Collectively from all three biological assays employed
herein, a number of conclusions can be drawn in terms of
structure–activity relationships within the epothilone
family. First, the addition of the C12 methyl group does
not enhance the activity in the trans-cyclopropyl series
(compound 5 vs 6, 7 vs 8, 9 vs 10), contrary to the result in
the cis epoxide series, where epothilone B (2) is at least
10-fold more active than epothilone A (1). This could be due
to the different orientation of the C12 methyl group in the cis
and trans compounds or to overall differences in confor-
mation between the cis and trans compounds, although the
details remain to be elucidated. Second, the introduction of
the 2-thiomethylthiazole side chain enhances the activity
compared with the natural 2-methylthiazole side chain
(compounds 2 vs 3, 5 vs 11, and 6 vs 12). This effect was
previously observed for epothilone C and D analogues.4
Third, the replacement of a methyl group with a thiomethyl
group in the pyridine side chain series (compounds 8 vs 13)
reduces potency, contrary to the results obtained for the
thiazole side chains above. This conclusion was based on
the cell cytotoxicity and in vitro tubulin polymerization
data, while in the fluorescent taxoid displacement assay the
replacement of the methyl group with a thiomethyl moiety
in the pyridine side chain is indifferent in terms of binding
affinity. This discrepancy may simply reflect differences in
cell uptake and permeability of the compounds tested or
differences in the sensitivity of the two tubulin assays.
Despite this discrepancy, it is clear from these data that the
introduction of a thiomethyl group at the thiazole side chain
is a more favorable modification than the introduction of a
thiomethyl group at the pyridine side chain, which may be
0.4
Paclitaxel
(1)
0.3
0.2
0.1
0.0
(2)
(3)
(4)
(8)
-9
-8
-7
-6
-5
-4
-3
Log [Competitor]0
Figure 2. Displacement of the fluorescent taxoid Flutax-2 (50 nM) from
microtubule binding sites (50 nM) by competing ligands at 378C. The dots
indicate acquired data points and the lines were generated so that they give
the best fit value of the binding equilibrium constant of each competitor,
assuming one-to-one binding to the same site. Ligands assayed are
paclitaxel (Taxolw) (dark blue), epothilone A (1) (red), epothilone B (2)
(violet), compound 3 (black), compound 4 (light brown), and compound 8
(green). Representative curves for selected epothilone analogues (3, 4, and
8) are presented in this figure to exemplify how the binding affinities were
measured for each compound in Table 3.

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6419
due to differing steric requirements by the two side chain
scaffolds. In agreement with previous data obtained with cis
pyridine epothilone analogues,18 relocation of the thio-
methyl group of the pyridine side chain from the position 5
(compound 13) to position 6 (compound 14) resulted in
significant loss of activity. Fourth, mixed results are
obtained with compounds 7 vs 9 and 8 vs 10 in which the
5-methylpyridine side chain (compounds 7 and 8) is
substituted by the 5-hydroxymethylpyridine side chain
(compounds 9 and 10). This substitution appears indifferent
in cytotoxicity assays against the 1A9 human ovarian
carcinoma cells (Table 1) where very similar IC50 values are
obtained for each pair (e.g. 0.6 and 0.7 nM for compounds 7
and 9, respectively; 1.7 nM for compounds 8 and 10). On
the other hand, in the human epidermoid carcinoma cells
KB-31, compound 10 is 2-fold more active than its
counterpart compound 8 with IC50s at 0.44 vs 0.9 nM,
respectively. Given the small differences in the growth rate
of the two human cancer cell lines that could account for the
differential results, we could conclude that the introduction
of the 5-hydroxymethylpyridine side chain is not likely to
enhance activity in, at least, trans-12,13-cyclopropyl
analogues of the epothilone family.
numbering (see Fig. 1). IR spectra were recorded on a
Perkin–Elmer 1600 series FT-IR spectrometer. High
resolution mass spectra were recorded on a PerSeptive
Biosystems Voyagere IonSpec mass spectrometer
(MALDI-FTMS) or on an API 100 Perkin–Elmer mass
spectrometer (ESI).
4.2. Synthesis of epothilone 3
4.2.1. Stille coupling of vinyl iodide 15 with stannane 16.
A solution of Pd2(dba)3·CHCl3 (3.9 mg, 3.8 mmol), AsPh3
(4.6 mg, 15 mmol), and CuI (7.2 mg, 38 mmol) in DMF
(degassed, 0.5 mL) was added at 258C to a solution of iodide
156 (10 mg, 19 mmol) and stannane 165 (11 mg, 38 mmol) in
DMF (degassed, 0.5 mL), and the resulting solution was
stirred for 2 h. Water (10 mL) was added, and the mixture
was extracted with EtOAc (3£10 mL). The combined
organic phase was washed with water (30 mL), brine
(30 mL), and dried (Na2SO4). After evaporation of the
volatiles, the residue was purified by flash column
chromatography (silica, hexanes/EtOAc 2:1!1:1) to yield
epothilone 3 as a white solid (7.2 mg, 72%); TLC Rf¼0.29
(silica, hexanes/EtOAc 1:1); [a ]2D2¼253 (c 0.51, CH2Cl2);
IR (film) nmax 3472 (br), 2967, 2920, 1731, 1684, 1461,
1420, 1378, 1249, 1143, 1032, 973, 879, 732, 667 cm21; 1H
NMR (600 MHz, CDCl3) d 1.00 (d, J¼ 7.0 Hz, 3H,
C(8)CH3), 1.08 (s, 3H, C(4)CaH3CbH3), 1.17 (d,
J¼6.5 Hz, 3H, C(6)CH3), 1.28 (s, 3H, C(4)CaH3CbH3),
1.36 (s, 3H, C(12)CH3), 1.36–1.56 (m, 6H, C(9)H2,
C(10)H2, C(11)H2), 1.67–1.75 (m, 1H, C(8)H), 1.91–1.97
(m, 1H, C(14)HaHb), 2.00–2.11 (m, 1H, C(14)HaHb), 2.13
(s, 3H, vinyl CH3), 2.39 (dd, J¼3.1, 14.0 Hz, 1H,
C(2)HaHb), 2.55 (dd, J¼10.1, 14.0 Hz, 1H, C(2)HaHb),
2.60 (br s, 1H, OH), 2.70 (s, 3H, thiazole CH3), 2.81 (dd,
J¼5.3, 7.0 Hz, 1H, C(13)H), 3.28–3.34 (m, 1H, C(6)H),
3.76–3.79 (m, 1H, C(7)H), 3.92 (br d, J¼6.1 Hz, 1H, OH),
4.15–4.20 (m, 1H, C(3)H), 5.43 (dd, J¼3.1, 7.5 Hz, 1H,
C(15)H), 6.52 (s, 1H, vinyl H), 7.00 (s, 1H, thiazole H); 13C
NMR (150 MHz, CDCl3, C(15) signal is obscured by the
chloroform peak.) d 13.8, 15.7, 16.7, 17.1, 20.2, 21.2, 22.5,
22.8, 30.7, 31.8, 32.1, 36.4, 39.1, 43.2, 52.8, 61.3, 61.5,
73.2, 74.3, 116.2, 119.2, 137.3, 152.5, 165.8, 170.6,
220.6; MALDI-FTMS m/z 562.2267 (MNaþ), calcd for
C27H41NO6S2Na 562.2267.
3. Conclusions
A series of epoxide and cyclopropane epothilones with
varying side chains were constructed by chemical synthesis
and biologically evaluated. These investigations led to the
identification of the thiomethylthiazole side chain as a
desirable pharmacophoric group improving the biological
activity of the epothilones with regard to cytotoxicity and
tubulin polymerizing properties. The enhanced activity was
confirmed by three distinct biological assays where the
effects of the compounds tested were determined both in
cells and in vitro. Further studies to expand this family of
potent epothilones in search of new drug candidates and
biological tools are in progress.
4. Experimental
4.1. General
4.3. Construction of aldehyde 32
All reactions were carried out under an argon atmosphere
with dry solvents under anhydrous conditions, unless
otherwise noted. Anhydrous solvents were obtained by
passing them through commercially available activated
alumina columns. All reagents were purchased at highest
commercial quality and used without further purification.
Reactions were generally monitored by thin-layer chroma-
tography carried out on 0.25 mm E. Merck silica gel plates
(60F-254). E. Merck silica gel (60, particle size 0.040–
0.063 mm) was used for flash column chromatography.
Preparative thin-layer chromatography (PTLC) separations
were carried out on 0.25, 0.50 or 1 mm E. Merck silica gel
plates (60F-254). Optical rotations were recorded on a
Perkin–Elmer 241 polarimeter. NMR spectra were recorded
on Bruker DRX-600, DRX-500, AMX-400 or Varian
Mercury-300 instruments and calibrated using residual
undeuterated solvents as an internal reference. All labeling
of carbon atoms, e.g. C15, refers to epothilone A (1)
4.3.1. Alcohol 23. To a solution of cyclopropyl alcohol 227
(4.08 g, 24 mmol) in DMF (40 mL) was added sodium
hydride (1.45 g, 36 mmol, 60% in mineral oil) portionwise
with stirring at 08C. After stirring for 0.5 h at 258C, the
mixture was cooled to 08C, benzyl bromide (4.3 mL,
36 mmol) was added over 2 min, and stirring was continued
for 12 h at 258C. The reaction was quenched with NH4Cl
(sat., 50 mL), the mixture was extracted with EtOAc
(3£50 mL) and the combined extract was washed with
brine (2£100 mL), dried (Na2SO4) and evaporated. The
residue was dissolved in CH2Cl2/MeOH 4:1 (60 mL), and
the solution was ozonized (100 L/h, ca. 5 g O3/h) at 2788C
for 21 min. (Note: Longer reaction times must be avoided to
prevent oxidation of the benzyl ether to the corresponding
benzoate.) Excess ozone was removed by flushing with N2
for 1 min, and then NaBH4 (2.75 g, 73 mmol) was added in

6420
K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
small portions (Caution! Exothermic!) followed by
methanol (20 mL). The mixture was warmed to 258C over
1 h, and the reaction was quenched by the addition of NH4Cl
(sat., 20 mL). The mixture was extracted with CH2Cl2
(2£50 mL), and the combined extract was washed with
brine (100 mL), dried (Na2SO4) and evaporated. The
residue was purified by flash chromatography (silica,
hexanes/EtOAc 5:2) to yield 23 as a yellow oil (5.07 g,
89%). TLC Rf¼0.20 (silica, hexanes/EtOAc 3:1); [a ]2D2¼
27.5 (c 1.76, CHCl3); IR (film) nmax 3390 (br), 2933, 2859,
1452, 1070, 739, 698 cm21; 1H NMR (400 MHz, CDCl3) d
0.12 (m, 1H, c-propyl CH2), 0.51 (dd, J¼4.4, 8.8 Hz, 1H,
c-propyl CH2), 0.92–1.00 (m, 1H, c-propyl CH), 1.07 (s,
3H, CH3), 1.15–1.24 (m, 1H, CH2), 1.39–1.48 (m, 1H,
CH2), 1.60–1.75 (m, 2H, CH2), 1.82 (br s, 1H, OH), 3.31
(dd, J¼8.8, 10.3 Hz, 1H, CH2OBn), 3.60 (dd, J¼6.0,
10.3 Hz, 1H, CH2OBn), 3.65 (t, J¼6.3 Hz, 2H, CH2OH),
4.50 (d, J¼12.0 Hz, 1H, OCH2Ph), 4.57 (d, J¼12.0 Hz,
1H, OCH2Ph), 7.28–7.36 (m, 5H, ArH); 13C NMR
(100 MHz, CDCl3) d 17.3, 17.8, 19.6, 23.5, 30.1, 37.8,
63.2, 71.1, 72.8, 127.7, 127.9, 128.5, 138.7; MALDI-
FTMS m/z 257.1519 (MNaþ), calcd for C15H22O2Na
257.1512.
mixture was stirred for 6 h at 08C, during which time a white
precipitate formed. The mixture was cooled to 2988C
(MeOH/N2(l) bath) and a solution of iodide 24 (5.16 g,
15.0 mmol) in THF (20 mL) was added over 0.5 h. The
reaction mixture was then allowed to warm to 2108C over
14 h, and then the reaction was quenched with NH4Cl
(sat., 10 mL). The mixture was extracted with EtOAc
(100 mLþ2£50 mL), the combined extract was dried
(Na2SO4) and evaporated, and the residue was purified by
flash chromatography (silica, hexanes/EtOAc 6:1!4:1) to
yield hydrazone 26 as a yellow oil (4.88 g, 84%). TLC
Rf¼0.38 (silica, hexanes/EtOAc 5:1); [a ]2D2¼261 (c 1.45,
1H NMR (500 MHz, CDCl3) d 0.09 (t, J¼5.0 Hz, 1H,
c-propyl CH2), 0.50 (dd, J¼4.4, 8.5 Hz, 1H, c-propyl CH2),
0.86–0.93 (m, 1H, c-propyl CH), 1.03 (s, 3H, CH3), 1.04
(d, J¼5.9 Hz, 3H, CHCH3), 1.20–1.24 (m, 2H, CH2),
1.30–1.44 (m, 4H, CH2), 1.75–1.81 (m, 1H, CH2), 1.84–
1.98 (m, 3H, CH2), 2.27–2.33 (m, 1H, CHCH3), 265–2.70
(m, 1H, NCHCH2OMe), 3.34–3.45 (m, 7H, CH2OCH3,
CH2OBn, CH2N), 3.51–3.60 (m, 2H, CH2OCH3, CH2OBn),
4.50 (d, J¼12.1 Hz, 1H, OCH2Ph), 4.55 (d, J¼11.8 Hz,
1H, OCH2Ph), 6.50 (d, J¼6.3 Hz, 1H, NvCH), 7.28–7.36
(m, 5H, ArH); 13C NMR (125 MHz, CDCl3) d 17.3, 17.7,
19.0, 19.8, 22.1, 23.1, 24.2, 26.5, 35.5, 37.1, 41.0, 50.5,
59.2, 63.5, 71.0, 72.4, 74.8, 127.4, 127.6, 128.3, 138.7,
144.6; MALDI-FTMS m/z 387.3008 (MHþ), calcd for
C24H39N2O2 387.3006.
CHCl3); IR (film) nmax 2926, 1454, 1097, 736, 697 cm21
;
4.3.2. Iodide 24. To a solution of cyclopropyl alcohol 23
(10.08 g, 43.0 mmol) in dry CH2Cl2 (100 mL) at 08C was
added methanesulfonyl chloride (4.2 mL, 54 mmol)
followed by triethylamine (9.0 mL, 65 mmol) dropwise. A
white precipitate started to form immediately. The mixture
was stirred at 258C for 1 h, then NH4Cl (sat., 50 mL) and
water (50 mL) were added and the phases were separated.
The aqueous phase was extracted with EtOAc (100 mL),
and the combined organic phase was washed with brine,
dried (Na2SO4) and evaporated. The residue was dissolved
in dry acetone (200 mL), and sodium iodide (19.3 g,
129 mmol) was added. The initially almost clear solution
was refluxed for 40 min, during which time a white
precipitate formed. Water (100 mL) was added and the
mixture was extracted with ether (500þ250 mL). The
combined extract was dried and evaporated, and the residue
was purified by flash chromatography (silica, hexanes/
EtOAc 5:1) to yield 24 as a colorless oil (14.16 g, 95%).
TLC Rf¼0.66 (silica, hexanes/EtOAc 5:1); [a]2D2¼216 (c
2.05, CHCl3); IR (film) nmax 2916, 2848, 1453, 1217, 1098,
4.3.4. Aldehyde 17. A solution of hydrazone 26 (3.82 g,
9.9 mmol) in iodomethane (10 mL) was heated at 608C
(reflux condenser) for 3 h, and was then cooled to 258C.
Excess iodomethane was evaporated and traces removed
under oil pump vacuum. The residual yellow syrup was
vigorously stirred with 3N HCl (190 mL) and pentane
(190 mL) for 3 h at 258C, the phases were separated, and the
aqueous phase was extracted with pentane (100 mL). The
combined organic phase was dried (Na2SO4, NaHCO3) and
evaporated to yield aldehyde 17 as a yellow oil (2.38 g,
88%). [a ]2D2¼þ2 (c 1.3, CHCl3); IR (film) nmax 2931, 2856,
;
1H NMR
1724, 1454, 1095, 1074, 736, 698 cm21
(500 MHz, CDCl3) d 0.12 (m, 1H, c-propyl CH2), 0.51
(dd, J¼4.6, 8.6 Hz, 1H, c-propyl CH2), 0.89–0.96 (m, 1H,
c-propyl CH), 1.04 (s, 3H, CH3), 1.08 (d, J¼7.0 Hz, 3H,
CHCH3), 1.16–1.24 (m, 1H, CH2), 1.26–1.33 (m, 1H,
CH2), 1.36–1.50 (m, 3H, CH2), 1.63–1.72 (m, 1H, CH2),
2.30–2.38 (m, 1H, CHCH3), 3.37 (dd, J¼8.3, 10.5 Hz, 1H,
CH2OBn), 3.57 (dd, J¼6.3, 10.3 Hz, 1H, CH2OBn), 4.51
(d, J¼11.9 Hz, 1H, OCH2Ph), 4.56 (d, J¼11.9 Hz, 1H,
OCH2Ph), 7.28–7.36 (m, 5H, ArH), 9.62 (d, J¼1.9 Hz, 1H,
CHO); 13C NMR (125 MHz, CDCl3) d 13.3, 17.2, 17.6,
19.6, 23.2, 24.0, 30.5, 41.0, 46.4, 71.0, 72.5, 127.4, 127.6,
128.3, 138.7, 205.3; MALDI-FTMS m/z 297.1830 (MNaþ),
calcd for C18H26O2Na 297.1825.
1
1073, 735, 697 cm21; H NMR (600 MHz, CDCl3) d 0.13
(m, 1H, c-propyl CH2), 0.55 (dd, J¼4.4, 8.8 Hz, 1H,
c-propyl CH2), 0.94–1.02 (m, 1H, c-propyl CH), 1.05 (s,
3H, CH3), 1.25–1.31 (m, 1H, CH2), 1.37–1.42 (m, 1H,
CH2), 1.90–2.00 (m, 2H, CH2), 3.23 (t, J¼7.0 Hz, 1H,
CH2I), 3.33 (dd, J¼8.8, 10.3 Hz, 1H, CH2OBn), 3.59 (dd,
J¼6.2, 10.3 Hz, 1H, CH2OBn), 4.50 (d, J¼11.8 Hz, 1H,
OCH2Ph), 4.56 (d, J¼11.8 Hz, 1H, OCH2Ph), 7.28–7.36
(m, 5H, ArH); 13C NMR (150 MHz, CDCl3) d 7.3, 17.2,
17.5, 18.9, 23.2, 31.1, 41.5, 70.9, 72.5, 127.5, 127.6, 128.3,
138.6; ESI-MS m/z 367 (MNaþ), calcd for C15H21IONa
367.
Due to the configurational lability at C8 (epothilone
numbering), the aldehyde should be used immediately in
the next step. The dr at C8 was estimated as follows: A
sample of 17 was treated with excess NaBH4 in methanol
for 10 min. The reaction was quenched with NH4Cl (sat.),
the mixture was extracted with EtOAc, and the extract was
dried (Na2SO4) and evaporated. The residue was treated
with (R )-(2)-MTPACl (2–3 equiv.), excess triethylamine
4.3.3. Hydrazone 26. A solution of LDA was prepared by
adding n-BuLi (13.1 mL, 21.0 mmol, 1.6 M in hexanes) to
diisopropylamine (2.94 mL, 21.0 mmol) in THF (10 mL) at
2788C, then warming the solution to 08C, and stirring for
10 min. To this LDA solution was added propionaldehyde
SAMP hydrazone 259c,10 (3.32 g, 19.5 mmol), and the

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6421
and 4-DMAP in CH2Cl2 for 3 h. Purification by prepara-
tive TLC yielded a sample of the (S)-MTPA ester, which
rated, and the residue was filtered through a plug of silica
eluting with hexane/ether 10:1. The filtrate was evaporated
and the resulting crude silyl ether (3.14 g, 4.0 mmol, 99%)
was dissolved in THF (40 mL). To this was added a cold
(08C) solution of HF·pyridine complex (6.4 mL) and
pyridine (18 mL) in THF (32 mL) at 08C (this solution
was prepared by slowly adding the HF·pyridine complex to
a solution of pyridine in THF at 08C; Caution! HF·pyridine
is highly corrosive. The addition of HF·pyridine to the
pyridine–THF solution is highly exothermic, and must be
done with stirring and cooling in ice bath to prevent
splashing), and the resulting solution was stirred at 258C for
4 h. The mixture was diluted with EtOAc (100 mL), placed
in an ice bath, and quenched by careful addition of NaHCO3
(sat., 100 mL) and as much solid NaHCO3 as needed to
ensure complete neutralization (Caution! Foaming!). The
mixture was extracted with EtOAc (3£100 mL), and the
combined extract was dried (Na2SO4) and evaporated, and
the residue was purified by flash chromatography (silica,
hexanes/EtOAc 5:1) to yield 28 as a colorless oil (2.40 g,
89%). TLC Rf¼0.39 (silica, hexanes/EtOAc 5:1);
[a ]2D2¼226 (c 1.1, CHCl3); IR (film) nmax 3458 (br),
2929, 2856, 1693, 1472, 1462, 1255, 1093, 986, 836,
1
by H NMR analysis showed a dr¼97:3, with the correct
absolute stereochemistry at C8 as the major isomer.11
Analogous results were obtained by using (S )-(þ)-
MTPACl.
4.3.5. Aldol product 27. A solution of LDA was prepared
by adding n-BuLi (7.5 mL, 12 mmol, 1.6 M in hexanes) to
diisopropylamine (1.68 mL, 12 mmol) in THF (12 mL) at
2788C, then warming the solution briefly to 08C, and finally
cooling back to 2788C. A solution of ketone 199c (4.63 g,
11.5 mmol) in THF (12 mL) was added dropwise over
2 min, and the mixture was stirred for 1 h at 2788C and then
for 0.5 h at 2408C. It was again cooled to 2788C, and a
solution of aldehyde 17 (1.37 g, 5.0 mmol) in THF (25 mL),
pre-cooled to 2788C, was added via cannula over 1 min,
taking care to ensure minimal warming during transfer. The
mixture was stirred for 5 min, and the reaction was then
quenched by rapid injection of a solution of AcOH (1.4 mL)
in THF (4.2 mL). After 5 min at 2788C, the mixture was
warmed to 258C and partitioned between NH4Cl (sat.,
50 mL) and ether (50 mL). The aqueous phase was
extracted with ether (2£50 mL), the combined extract was
dried (Na2SO4) and evaporated, and the residue was purified
by flash chromatography (silica, hexanes/ether 20:1!6:1)
to yield recovered ketone 19 (1.71 g, 4.25 mmol) followed
by the aldol product 27 in diastereomerically pure form
(2.73 g, 81%). TLC Rf¼0.34 (silica, hexanes/EtOAc 5:1);
[a]2D2¼240 (c 1.0, CHCl3); IR (film) nmax 3502 (br), 2954,
775 cm21 1H NMR (500 MHz, CDCl3) d 0.08 (s, 9H,
;
CH3Si), 0.08–0.13 (m, 4H, CH3Si, c-propyl CH2), 0.49 (dd,
J¼4.4, 8.8 Hz, 1H, c-propyl CH2), 0.88–0.92 (m, 19H,
(CH3)3CSi, c-propyl CH), 0.93 (d, J¼6.6 Hz, 3H, CH2-
CHCH3), 1.01–1.25 (m, 4H, CH2), 1.03 (s, 3H, CH3), 1.06
(d, J¼5.9 Hz, 3H, C(O)CHCH3), 1.07 (s, 3H, CH3), 1.23 (s,
3H, CH3), 1.29–1.38 (m, 2H, CH2CHCH3, CH2), 1.42–1.52
(m, 1H, CH2), 1.56–1.63 (m, 2H, CH2CH2OH), 2.01 (s, 1H,
OH), 3.10–3.17 (m, 1H, C(O)CHCH3), 3.40 (dd, J¼8.1,
10.3 Hz, 1H, CH2OBn), 3.53 (dd, J¼6.6, 10.3 Hz, 1H,
CH2OBn), 3.62–3.67 (m, 2H, CH2OH), 3.79–3.83 (m, 1H,
C(O)CH(CH3)CHOTBS), 4.07 (dd, J¼4.2, 6.1 Hz, 1H,
CH(OTBS)CH2CH2OH), 4.51 (d, J¼12.1 Hz, 1H,
OCH2Ph), 4.55 (d, J¼12.1 Hz, 1H, OCH2Ph), 7.27–7.36
(m, 5H, ArH); 13C NMR (125 MHz, CDCl3) d 24.0, 23.9,
23.8, 23.7, 15.6, 17.3, 17.6, 17.7, 18.2, 18.5, 19.8, 23.1,
24.7, 24.8, 26.0, 26.2, 31.0, 38.3, 38.9, 41.7, 45.0,
53.7, 60.2, 71.0, 72.4, 73.0, 127.4, 127.6, 128.3, 138.7,
219.5; MALDI-FTMS m/z 699.4807 (MNaþ), calcd for
C39H72O5Si2Na 699.4816.
1
2928, 2856, 1681, 1472, 1255, 1098, 836, 776 cm21; H
NMR (500 MHz, CDCl3) d 0.05 (s, 6H, CH3Si), 0.08–0.10
(m, 4H, CH3Si, c-propyl CH2), 0.11 (s, 3H, CH3Si), 0.51
(dd, J¼4.4, 8.8 Hz, 1H, c-propyl CH2), 0.84 (d, J¼7.0 Hz,
3H, CH2CHCH3), 0.87–0.92 (m, 1H, c-propyl CH), 0.90 (s,
9H, (CH3)3CSi), 0.91 (s, 9H, (CH3)3CSi), 1.02–1.08 (m,
1H, CH2), 1.03 (d, J¼5.9 Hz, 3H, C(O)CHCH3), 1.04 (s,
3H, CH3), 1.09 (s, 3H, CH3), 1.12–1.18 (m, 1H, CH2) 1.21
(s, 3H, CH3), 1.25–1.33 (m, 2H, CH2), 1.45–1.56 (m, 3H,
CH2CHCH3, CH2), 1.61–1.68 (m, 1H, CH2CH2OTBS),
1.70–1.79 (m, 1H, CH2), 3.28–3.33 (m, 2H,
C(O)CH(CH3)CHOH), 3.40 (dd, J¼8.1, 10.3 Hz, 1H,
CH2OBn), 3.52 (s, 1H, OH), 3.54 (dd, J¼6.6, 10.3 Hz,
1H, CH2OBn), 3.59–3.64 (m, 1H, CH2OTBS), 3.66–3.71
(m, 1H, CH2OTBS), 3.99 (dd, J¼2.6, 7.3 Hz, 1H,
CHOTBS), 4.51 (d, J¼12.1 Hz, 1H, OCH2Ph), 4.56 (d,
J¼12.1 Hz, 1H, OCH2Ph), 7.26–7.36 (m, 5H, ArH); 13C
NMR (125 MHz, CDCl3) d 25.3, 24.1, 23.8, 9.6, 15.3,
17.3, 17.7, 18.2, 18.3, 19.8, 20.4, 22.8, 23.1, 23.9, 25.9,
26.1, 32.9, 35.6, 37.8, 41.2, 41.5, 53.9, 60.4, 71.0, 72.3,
74.0, 74.9, 127.4, 127.6, 128.2, 138.8, 222.3; MALDI-
FTMS m/z 699.4796 (MNaþ), calcd for C39H72O5Si2Na
699.4816.
4.3.7. Ester 29. The alcohol 28 (2.40 g, 3.5 mmol), Dess–
Martin periodinane (3.75 g, 8.8 mmol), NaHCO3 (0.74 g,
8.8 mmol) and water (76 mL, 4.2 mmol) were mixed in
CH2Cl2 (80 mL), and the resulting suspension was stirred
for 1 h. The mixture was diluted with ether (200 mL), water
(100 mL) and NaHCO3 (sat., 100 mL), and was then
filtered. The phases were separated and the aqueous phase
was extracted with ether (2£100 mL). The combined
extract was dried (Na2SO4) and evaporated, and the residue
was filtered through a plug of silica eluting with
hexanes/EtOAc 6:1. The filtrate was evaporated and the
resulting crude aldehyde (2.15 g, 3.2 mmol, 90%) was
dissolved in a mixture of THF (80 mL), t-BuOH (145 mL)
and 2-methyl-2-butene (25 mL). To this solution was added
a solution of NaH2PO4 (0.95 g, 6.7 mmol) and NaClO2
(1.14 g, 10 mmol) in water (31 mL), and the resulting
mixture was stirred vigorously for 1 h. The volatiles were
removed by evaporation, and the residue was partitioned
between EtOAc (100 mL) and brine (100 mL). The phases
4.3.6. Alcohol 28. A solution of aldol product 27 (2.71 g,
4.0 mmol) and 2,6-lutidine (1.40 mL, 12 mmol) in CH2Cl2
(25 mL) was cooled to 2208C and then TBSOTf (1.84 mL,
8.0 mmol) was added dropwise. The mixture was stirred for
1 h at 2208C and the reaction was then quenched by the
addition of NH4Cl (sat., 25 mL). The mixture was warmed
to 258C, the phases were separated and the aqueous phase
was extracted with CH2Cl2 (25 mL) and ether (25 mL). The
combined organic phase was dried (Na2SO4) and evapo-

6422
K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
were separated and the aqueous phase was extracted with
EtOAc (3£100 mL). The combined extract was dried
(Na2SO4) and evaporated, and the residue was dissolved
in DMF (5 mL) and evaporated again to remove traces of
t-BuOH. The so obtained crude acid (2.4 g, ca. 3.2 mmol
.100%,) was again dissolved in DMF (10 mL), to which
2-(trimethylsilyl)ethanol (1.83 mL, 12.7 mmol), EDC
(0.92 g, 4.8 mmol), and 4-DMAP (40 mg, 0.33 mmol)
were added. The resulting suspension was stirred for 14 h,
after which time a clear solution was obtained. Water
(10 mL) was added and the mixture was extracted with ether
(3£50 mL). The combined extract was washed with
water–brine mixture (100þ100 mL), dried (Na2SO4) and
evaporated. The residue was purified by flash chroma-
tography (silica, hexanes/EtOAc 10:1) to yield ester 29 as a
viscous, pale yellow oil (2.08 g, 74%). TLC Rf¼0.57
(silica, hexanes/EtOAc 10:1); [a ]2D2¼233 (c 1.2, CHCl3);
IR (film) nmax 2954, 2930, 2856, 1735, 1695, 1472, 1385,
0.03–0.06 (m, 18H, CH3Si), 0.10 (s, 3H, CH3Si), 0.87 (s,
9H, (CH3)3CSi), 0.90 (s, 9H, (CH3)3CSi), 0.91 (d,
J¼6.6 Hz, 3H, CH2CHCH3), 0.98 (t, J¼8.6 Hz, 2H,
CH2CH2TMS), 1.04 (d, J¼7.0 Hz, 3H, C(O)CHCH3),
1.05–1.11 (m, 2H, CH2, c-propyl CH2), 1.06 (s, 3H,
CH3), 1.19–1.29 (m, 2H, CH2), 1.23 (s, 3H, CH3), 1.24 (s,
3H, CH3), 1.31–1.39 (m, 4H, c-propyl CH2, CH2CHCH3,
CH2), 1.43–1.52 (m, 1H, CH2), 1.67–1.71 (m, 1H, c-propyl
CH), 2.23 (dd, J¼6.6, 16.5 Hz, 1H, CH2CO2TMSE), 2.42
(dd, J¼3.3, 16.3 Hz, 1H, CH2CO2TMSE), 3.11–3.16 (m,
1H, C(O)CHCH3), 3.76 (dd, J¼1.9, 7.2 Hz, 1H,
C(O)CH(CH3)CHOTBS), 4.09–4.20 (m, 2H, CH2CH2-
TMS), 4.38 (dd, J¼3.3, 6.6 Hz, 1H, CH(OTBS)CH2CO2-
TMSE), 9.36 (d, J¼5.5 Hz, 1H, CHO); 13C NMR
(125 MHz, CDCl3) d 24.7, 24.5, 23.8, 23.7, 21.6, 15.5,
17.2, 17.3, 17.7, 18.2, 18.5, 19.6, 22.6, 22.8, 23.4, 24.6, 26.0,
26.2, 30.1, 30.8, 31.6, 35.8, 38.8, 40.4, 41.3, 45.3, 53.4, 62.7,
73.8, 77.6, 172.1, 201.5, 217.7; MALDI-FTMS m/z 721.4671
(MNaþ), calcd for C37H74O6Si3Na 721.4685.
1252, 1090, 988, 836, 776 cm21 1H NMR (500 MHz,
;
CDCl3) d 0.04–0.06 (m, 18H, CH3Si), 0.10–0.12 (m, 4H,
CH3Si, c-propyl CH2), 0.50 (dd, J¼4.4, 8.4 Hz, 1H,
c-propyl CH2), 0.85–0.93 (m, 22H, (CH3)3CSi, c-propyl
CH, CH2CHCH3), 0.99 (t, J¼8.6 Hz, 2H, CH2CH2TMS),
1.03 (s, 3H, CH3), 1.05 (d, J¼7.0 Hz, 3H, C(O)CHCH3),
1.05–1.10 (m, 1H, CH2), 1.07 (s, 3H, CH3), 1.16–1.22 (m,
3H, CH2), 1.24 (s, 3H, CH3), 1.31–1.38 (m, 2H,
CH2CHCH3, CH2), 1.44–1.50 (m, 1H, CH2), 2.25 (dd,
J¼6.6, 16.5 Hz, 1H, CH2CO2TMSE), 2.43 (dd, J¼3.3,
16.5 Hz, 1H, CH2CO2TMSE), 3.12–3.18 (m, 1H,
C(O)CHCH3), 3.40 (dd, J¼8.1, 10.3 Hz, 1H, CH2OBn),
3.53 (dd, J¼6.6, 10.3 Hz, 1H, CH2OBn), 3.77 (dd, J¼1.6,
6.8 Hz, 1H, C(O)CH(CH3)CHOTBS), 4.10–4.21 (m,
2H, CH2CH2TMS), 4.39 (dd, J¼3.3, 6.6 Hz, 1H,
CH(OTBS)CH2CO2TMSE), 4.51 (d, J¼12.1 Hz, 1H,
OCH2Ph), 4.55 (d, J¼12.1 Hz, 1H, OCH2Ph), 7.27–7.36
(m, 5H, ArH); 13C NMR (125 MHz, CDCl3) d 24.7, 24.4,
23.8, 23.7, 21.5, 15.4, 17.2, 17.3, 17.7, 17.8, 18.2, 18.5,
19.6, 19.8, 23.2, 23.5, 24.8, 26.0, 26.2, 31.0, 39.0, 40.4,
41.8, 45.1, 53.4, 62.7, 71.0, 72.4, 73.9, 77.5, 127.4, 127.6,
128.3, 138.7, 172.2, 217.9; MALDI-FTMS m/z 813.5315
(MNaþ), calcd for C44H82O6Si3Na 813.5311.
4.3.9. Enol ether 31. To a suspension of MeOCH2PPh3Cl
(3.09 g, 9.0 mmol) in THF (20 mL) at 08C was added
NaHMDS (8.5 mL, 8.5 mmol, 1 M in THF) dropwise. A red
color developed. The mixture was stirred at 08C for 0.5 h
and it was then cooled to 2408C. A solution of aldehyde 30
(2.12 g, 3.0 mmol) in THF (7 mL) was added, and the
mixture was allowed to warm to 2108C over 2 h. The
reaction was quenched with NH4Cl (sat., 15 mL), the phases
were separated, and the aqueous phase was extracted with
EtOAc (2£75 mL). The combined extract was dried
(Na2SO4) and evaporated, and the residue was purified by
flash chromatography (silica, hexanes/EtOAc 30:1) to yield
enol ether 31 as a colorless, viscous oil (1.85 g, 84%, olefin
cis:trans ca. 1:1 by 1H NMR). TLC Rf¼0.23 (silica,
hexanes/EtOAc 30:1); [a ]2D2¼236 (c 1.2, CHCl3); IR
(film) nmax 2954, 2930, 2856, 1735, 1695, 1251, 1171, 1105,
988, 836, 776 cm21 1H NMR (500 MHz, CDCl3, total
;
integral normalized to 78H) d 0.03–0.06 (m, 18H, CH3Si),
0.11 (s, 3H, CH3Si), 0.14–0.20 (m, 1H, c-propyl CH2), 0.53
(dd, J¼4.4, 8.5 Hz, 0.5H, c-propyl CH2), 0.66 (dd, J¼4.2,
8.6 Hz, 0.5H, c-propyl CH2), 0.85–0.92 (m, 21H,
(CH3)3CSi, CH2CHCH3), 0.96–1.01 (m, 5H, CH3,
CH2CH2TMS), 1.03–1.07 (m, 6H, CH3, C(O)CHCH3),
1.07–1.12 (m, 2.5H, CH2, c-propyl CH), 1.19–1.37 (m, 4H,
CH2, CH2CHCH3), 1.23 (s, 3H, CH3), 1.40–1.51 (m, 1.5H,
CH2, c-propyl CH), 2.21–2.26 (m, 1H, CH2CO2TMSE),
2.43 (dd, J¼3.3, 16.5 Hz, 1H, CH2CO2TMSE), 3.10–3.18
(m, 1H, C(O)CHCH3), 3.50 (s, 1.5H, OCH3), 3.61 (s, 1.5H,
OCH3), 3.75–3.78 (m, 1H, C(O)CH(CH3)CHOTBS),
4.09 (dd, J¼6.3, 9.4 Hz, 0.5H, cis-HCvC(H)OCH3),
4.10–4.20 (m, 2H, CH2CH2TMS), 4.37–4.40 (m, 1H,
CH(OTBS)CH2CO2TMSE), 4.61 (dd, J¼7.5, 12.5 Hz,
0.5H, trans-HCvC(H)OCH3), 5.96 (dd, J¼1.1, 6.3 Hz,
0.5H, cis-HCvC(H )OCH3), 6.33 (d, J¼12.5 Hz, 0.5H,
trans-HCvC(H )OCH3); 13C NMR (125 MHz, CDCl3,
more than one set of peaks counted due to the presence of
E- and Z-isomers) d 24.7, 24.5, 23.8, 23.7, 21.5, 14.1,
15.4, 15.5, 17.2, 17.6, 17.7, 18.1, 18.2, 18.5, 19.6, 19.7,
20.8, 21.5, 21.6, 22.3, 22.6, 22.8, 23.4, 23.5, 24.7, 24.8,
26.0, 26.2, 31.0, 31.6, 38.9, 40.4, 41.5, 45.1, 45.2 53.4, 56.1,
59.6, 62.7, 73.8, 73.9, 77.5, 77.6, 103.0, 106.9, 146.7, 147.7,
172.1, 217.8, 217.9; MALDI-FTMS m/z 749.4996 (MNaþ),
calcd for C39H78O6Si3Na 749.4998.
4.3.8. Aldehyde 30. To a solution of benzyl ether 29 (2.08 g,
2.63 mmol) in EtOH/EtOAc 1:1 (50 mL) was added 20%
Pd(OH)2 on carbon (2.1 g, 60% moisture), and the mixture
was hydrogenated for 1 h H2, 1 atm. It was then filtered
through celite to remove the catalyst, the filtrate was
evaporated, and the residue was co-evaporated with benzene
to remove traces of EtOH. The resulting crude alcohol
(1.89 g, ca. 2.6 mmol, .100%) was dissolved in CH2Cl2
(60 mL), Dess–Martin periodinane (2.76 g, 6.5 mmol),
NaHCO3 (0.55 g, 6.5 mmol) and water (56 mL, 3.1 mmol)
were added, and the resulting suspension was stirred for 1 h.
The mixture was diluted with ether (150 mL), water
(75 mL) and NaHCO3 (sat., 75 mL), and was then filtered.
The phases were separated and the aqueous phase was
extracted with ether (2£75 mL). The combined extract was
dried (Na2SO4) and evaporated, and the residue was purified
by flash chromatography (silica, hexanes/EtOAc 15:1) to
yield aldehyde 30 as a viscous oil (1.55 g, 84%). TLC
Rf¼0.24 (silica, hexanes/EtOAc 15:1); [a]2D2¼247 (c 1.3,
CHCl3); IR (film) nmax 2954, 2856, 1734, 1703, 1251, 1173,
1
1084, 988, 837, 776 cm21; H NMR (500 MHz, CDCl3) d

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6423
4.3.10. Aldehyde 32. To a solution of enol ether 31
(847 mg, 1.16 mmol) in dioxane:water 9:1 (12mL) was
added pyridinium para-toluenesulfonate (2.34 g, 9.31
mmol) and the mixture was stirred at 708C until TLC
indicated the completion of the reaction (6–10 h). The
reaction was then quenched with NaHCO3 (sat., 15 mL),
and the mixture was extracted with EtOAc (3£50 mL). The
combined extract was dried (Na2SO4) and evaporated, and
the residue was purified by flash chromatography (silica,
hexanes/EtOAc 15:1) to yield 32 as a colorless, viscous oil
(681 mg, 82%). TLC Rf¼0.29 (silica, hexanes/EtOAc
15:1); [a ]2D2¼234 (c 1.0, CHCl3); IR (film) nmax 2954,
CuI (13 mg, 70 mmol) under Ar(g), and then the inert
atmosphere was replaced by propyne (1 atm, balloon). The
mixture was stirred at 258C for 3 h. During this time, a
precipitate formed, and the reaction mixture turned dark
brown. Water (15 mL) was added, the mixture was
extracted with EtOAc, and the combined extract was dried
(Na2SO4) and evaporated. The pure 1-arylpropyne was
obtained by flash chromatography (silica, hexane:EtOAc
mixtures).
4.4.3. Propynylpyridine 35. Brown foam (96%); TLC
Rf¼0.23 (silica, hexanes/EtOAc 5:1); IR (film) nmax 3057,
1
1
2856, 1731, 1695, 1251, 1086, 988, 836, 776 cm21; H
2229, 1594, 1560, 1478, 1448, 1075, 702 cm21; H NMR
NMR (600 MHz, CDCl3) d 0.03–0.07 (m, 19H, CH3Si,
c-propyl CH2), 0.11 (s, 3H, CH3Si), 0.57 (dd, J¼4.6,
8.6 Hz, 1H, c-propyl CH2), 0.77–0.84 (m, 1H, c-propyl
CH), 0.88 (s, 9H, (CH3)3CSi), 0.90 (s, 9H, (CH3)3CSi),
0.92 (d, J¼7.0 Hz, 3H, CH2CHCH3), 0.95–0.99 (m, 2H,
CH2CH2TMS), 1.00 (s, 3H, CH3), 1.04 (d, J¼7.0 Hz, 3H,
C(O)CHCH3), 1.07 (s, 3H, CH3), 1.09–1.22 (m, 2H, CH2),
1.23 (s, 3H, CH3), 1.26–1.36 (m, 4H, CH2CHCH3, CH2),
1.42–1.50 (m, 1H, CH2), 2.24 (dd, J¼6.8, 16.5 Hz, 1H,
CH2CO2TMSE), 2.36 (ddd, J¼2.2, 7.4, 17.2 Hz, 1H,
CH2CHO), 2.42 (m, 2H, CH2CHO, CH2CO2TMSE),
3.12–3.17 (m, 1H, C(O)CHCH3), 3.77 (dd, J¼1.7,
7.0 Hz, 1H, C(O)CH(CH3)CHOTBS), 4.10–4.20 (m,
2H, CH2CH2TMS), 4.39 (dd, J¼3.3, 6.8 Hz, 1H,
CH(OTBS)CH2CO2TMSE), 9.81 (t, J¼2.2 Hz, 1H,
CHO); 13C NMR (150 MHz, CDCl3) d 24.7, 24.4,
23.7, 23.6, 21.5, 15.5, 16.8, 17.2, 17.6, 17.7, 18.2,
18.5, 19.0, 19.6, 23.5, 24.8, 26.0, 26.2, 31.0, 38.9,
40.4, 41.7, 44.1, 45.2, 53.4, 62.7, 73.9, 77.6, 172.2, 202.6,
217.9; MALDI-FTMS m/z 735.4823 (MNaþ), calcd for
C38H76O6Si3Na 735.4842.
(500 MHz, CDCl3) d 2.09 (s, 3H, CH3), 4.21 (s, 2H, CH2),
7.26–7.35 (m, 10H, ArH), 7.48–7.51 (m, 6H, ArH), 7.67
(m, 1H, ArH), 8.47 (d, J¼1.5 Hz, 1H, ArH); 13C NMR
(150 MHz, CDCl3) d 4.3, 63.3, 79.5, 86.3, 87.3, 126.1,
127.2, 127.9, 128.5, 133.2, 134.8, 142.6, 143.6, 148.6;
MALDI-FTMS m/z 390.1851 (MHþ), calcd for C28H24NO
390.1852.
4.4.4. Pyridine 36. A solution of trityl ether 35 (1.38 g,
3.54 mmol) in CHCl3 (15 mL) was cooled to 08C and then
saturated with HCl (g). After 1 h at 08C, the reaction was
quenched by the addition of NaHCO3 (sat., 50 mL), and the
phases were separated. The aqueous phase was extracted
with CH2Cl2 (50 mL) and the combined organic phase was
dried (Na2SO4) and evaporated. Flash chromatography
(silica, hexanes/EtOAc 1:2þ5% MeOH) afforded 5-hydroxy-
methyl-2-prop-1-ynylpyridine as a yellow, viscous oil
(0.36 g, 69%). TLC Rf¼0.29 (silica, hexanes/EtOAc
1:2þ5% MeOH); IR (film) nmax 3262, 2916, 2230, 1596,
1561, 1023, 838 cm21; 1H NMR (500 MHz, CDCl3) d 2.02
(s, 3H, CH3), 4.23 (br s, 1H, OH), 4.67 (s, 2H, CH2), 7.30 (d,
J¼8.1 Hz, 1H, ArH), 7.62 (dd, J¼2.2, 8.1 Hz, 1H, ArH),
8.37 (d, J¼2.2 Hz, 1H, ArH); 13C NMR (125 MHz, CDCl3)
d 4.2, 61.8, 79.1, 86.9, 126.4, 135.0, 135.7, 142.3, 148.0;
MALDI-FTMS m/z 148.0754 (MHþ), calcd for C9H10NO
148.0757. To a solution of this alcohol (0.40 g, 2.7 mmol) in
THF (10 mL) at 08C was added NaH (0.13 g, 3.3 mmol,
60% in oil). After stirring for 5 min, chloromethyl methyl
ether (0.25 mL, 3.3 mmol) was added, and the mixture was
stirred at 08C for 1 h. The reaction was then quenched with
NaCl (sat.), and a few drops of NaOH (1 M) were added.
The mixture was extracted with EtOAc (3£50 mL), the
combined extract was dried (Na2SO4) and evaporated, and
the residue was purified by flash chromatography (silica,
hexanes/EtOAc 1:1) to yield 36 as a pale yellow oil (0.26 g,
50%). TLC Rf¼0.41 (silica, hexanes/EtOAc 1:1); IR (film)
4.4. Construction of vinyl iodides 20c–g
4.4.1. 2-Bromo-5-[(trityloxy)methyl]pyridine 34. Trityl
chloride (3.90 g, 14 mmol), 4-DMAP (2.08 g, 17 mmol) and
2-bromo-5-hydroxymethylpyridine 3312 (1.88 g, 10 mmol)
were dissolved in DMF (15 mL) and the solution was stirred
at 808C for 48 h. A white precipitate formed during this
time. After cooling, the mixture was diluted with NaHCO3
(sat., 25 mL) and extracted with EtOAc (3£50 mL). The
combined extract was washed with brine, with a few drops
of NaOH (1 M) added (2£100 mL). After drying and
evaporation, the solid residue was purified by flash
chromatography (silica, hexanes/EtOAc 15:1) to yield 34
as a white solid (4.46 g, 100%). TLC Rf¼0.30 (silica,
hexanes/EtOAc 15:1); IR (film) nmax 3057, 1448, 1086, 764,
700, 632 cm21; 1H NMR (400 MHz, CDCl3) d 4.18 (s, 2H,
CH2), 7.24–7.36 (m, 10H, ArH), 7.44–7.49 (m, 6H, ArH),
7.57 (dd, J¼2.1, 8.2 Hz, 1H, ArH), 8.32 (d, J¼2.6 Hz,
1H, ArH); 13C NMR (100 MHz, CDCl3) d 62.8, 87.5,
127.2, 127.3, 128.0, 128.5, 133.9, 137.4, 140.7, 143.5,
148.8; MALDI-FTMS m/z 430.0792 (MHþ), calcd for
C25H21BrNO 430.0801.
n
max 2947, 2230, 1595, 1560, 1478, 1149, 1104, 1047, 919,
830 cm21 1H NMR (500 MHz, CDCl3) d 2.09 (s, 3H,
;
CH3CuC), 3.40 (s, 3H, CH3O), 4.60 (s, 2H, OCH2O), 4.71
(s, 2H, ArCH2O), 7.36 (d, J¼7.7 Hz, 1H, ArH), 7.63 (dd,
J¼1.8, 7.7 Hz, 1H, ArH), 8.52 (d, J¼7.8 Hz, 1H, ArH); 13C
NMR (125 MHz, CDCl3) d 4.77, 55.9, 66.9, 79.9, 96.4,
126.7, 132.6, 136.0, 143.6, 149.7; MALDI-FTMS m/z
192.1014 (MHþ), calcd for C11H14NO2 192.1019.
4.4.2. Sonogashira coupling of aryl bromides (34, 37–39)
with propyne (general procedure). To a briefly deoxy-
genated (Ar bubbling) solution of the aryl bromide 34, 37,
38, or 39 (3.5 mmol) in DMF (3 mL) and diisopropyl amine
(2.5 mL) were added Pd(PPh3)2Cl2 (25 mg, 36 mmol) and
4.4.5. Sonogashira coupling product from 37. The
reaction was very slow, probably due to Pd coordination
to the thioether moiety; therefore, 10 mol% Pd(PPh3)2Cl2
and 20 mol% CuI were used. The product was obtained as a
brown oil (42%). TLC Rf¼0.37 (silica, hexanes/EtOAc

6424
K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
15:1); IR (film) nmax 3110, 2914, 2240, 1493, 1417, 1278,
1
4.4.9. Vinyl iodide 20c. White cloudy film (80%). TLC
Rf¼0.25 (silica, hexanes/EtOAc 20:1); IR (film) nmax 3060,
2919, 1619, 1596, 1484, 1443, 1373, 1214, 1061, 985, 873,
1037, 966, 735 cm21; H NMR (400 MHz, CDCl3) d 2.06
(s, 3H, CuCCH3), 2.71 (s, 3H, SCH3), 7.19 (s, 1H, CH);
13C NMR (100 MHz, CDCl3) d 4.3, 16.4, 73.7, 86.4, 120.3,
137.7, 165.9; MALDI-FTMS m/z 170.0092 (MHþ), calcd
for C7H8NS2 170.0093.
1
761, 703, 632 cm21; H NMR (400 MHz, CDCl3) d 2.99
(d, J¼1.5 Hz, 3H, CH3C(I)¼C), 4.18 (s, 2H, CH2O), 7.10
(d, J¼8.2 Hz, 1H, pyridine ArH), 7.23–7.35 (m, 10H, trityl
ArH, CHvC), 7.47–7.51 (m, 6H, trityl ArH), 7.66 (dd,
J¼1.8, 8.2 Hz, 1H, pyridine ArH), 8.56 (d, J¼1.8 Hz, 1H,
pyridine ArH); 13C NMR (100 MHz, CDCl3) d 30.5, 63.5,
87.3, 105.0, 123.5, 127.2, 127.9, 128.6, 132.6, 135.2, 139.3,
143.7, 148.0, 154.8; MALDI-FTMS m/z 518.0990 (MHþ),
calcd for C28H25INO 518.0975.
4.4.6. Sonogashira coupling product from 38. Brown oil
(97%); TLC Rf¼0.21 (silica, hexanes/EtOAc 5:1); IR (film)
n
max 2908, 2226, 1567, 1531, 1461, 1431, 1361, 1108, 1008,
832 cm21 1H NMR (400 MHz, CDCl3) d 2.05 (s, 3H,
;
CuCCH3), 2.48 (s, 3H, SCH3), 7.24 (d, J¼8.2 Hz, 1H,
ArH), 7.44 (d, J¼8.2 Hz, 1H, ArH), 8.38 (s, 1H, ArH); 13C
NMR (100 MHz, CDCl3) d 4.3, 15.5, 79.2, 86.7, 126.2,
133.8, 134.4, 140.1, 147.4; MALDI-FTMS m/z 164.0527
(MHþ), calcd for C9H10NS 164.0528.
4.4.10. Vinyl iodide 20d. Yellow oil (67%). TLC Rf¼0.51
(silica, hexanes/EtOAc 4:1); IR (film) nmax 2924, 1716,
1619, 1596, 1481, 1372, 1211, 1149, 1102, 1045, 918, 873,
;
609, 517 cm21 1H NMR (600 MHz, CDCl3) d 2.97
4.4.7. Sonogashira coupling product from 39. Yellow oil
(70%); TLC Rf¼0.36 (silica, hexanes/EtOAc 20:1); IR
(film) nmax 2924, 2231, 1566, 1554, 1431, 1156, 1140,
(d, J¼1.7 Hz, 3H, CH3C(I)vC), 3.40 (s, 3H, OCH3), 4.57
(s, 2H, CH2O), 4.70 (s, 2H, CH2O), 7.10 (d, J¼7.9 Hz, 1H,
ArH), 7.24 (d, J¼1.7 Hz, 1H, HCvC), 7.65 (d, J¼7.9 Hz,
1H, ArH), 8.55 (s, 1H, ArH); 13C NMR (125 MHz, CDCl3)
d 30.5, 55.5, 66.5, 95.9, 105.4, 123.5, 131.3, 135.9, 139.2,
148.8, 155.4; MALDI-FTMS m/z 320.0142 (MHþ), calcd
for C11H15INO2 320.0142.
790 cm21 1H NMR (300 MHz, CDCl3) d 2.11 (s, 3H,
;
CuCCH3), 2.58 (s, 3H, SCH3), 7.06 (d, J¼7.8 Hz, 1H,
ArH), 7.08 (d, J¼7.8 Hz, 1H, ArH), 7.41 (t, J¼7.8 Hz, 1H,
ArH); 13C NMR (75 MHz, CDCl3) d 4.6, 13.4, 79.6, 86.7,
120.1, 122.3, 135.6, 143.3, 160.0; MALDI-FTMS m/z
164.0526 (MHþ), calcd for C9H10NS 164.0528.
4.4.11. Vinyl iodide 20e. The intermediate vinyl stannane is
readily protodestannylated; therefore, flash chromatography
of this intermediate must be performed using hexanes/
EtOAc/Et3N 50:1:1 as eluent, and the so obtained
vinylstannane contained other butyl tin compunds. Follow-
ing the general procedure, the mixture was treated with
enough I2 that the brown color persisted at the end of the
addition (ca. 2 equiv. of I2). After flash chromatography
(hexanes/EtOAc 50:1), vinyl iodide 20e was obtained as a
yellow oil (74%). TLC Rf¼0.41 (silica, hexanes/EtOAc
50:1); IR (film) nmax 3102, 2923, 1620, 1423, 1300, 1065,
4.4.8. Hydrostannylation–iodination (general pro-
cedure). This is an adaption of the previously reported
procedure.14 To a solution of hexabutylditin (10.1 mL,
20 mmol) in dry THF (40 mL) at 2788C was added n-BuLi
(12.9 mL, 20 mmol, 1.55 M in hexanes), and the resulting
clear solution was stirred at 2408C for 30 min. It was then
transferred via cannula to a suspension of CuCN (0.90 g,
10 mmol) in THF (2 mL) at 2788C. A clear yellow solution
formed, and it was stirred for 5 min at 2408C before being
re-cooled to 2788C. Then dry methanol (23 mL, 0.57 mol)
was added to yield a red solution, which was stirred at
2408C for 15 min, after which a solution of the arylpropyne
(5.0 mmol) in THF (5 mL) was added. The orange–red
solution was stirred at 2108C overnight (some Cu and/or
Cu2þ salts precipitate), then cooled to 2208C, followed by
the addition of methanol (10 mL). After 15 min at 2208C,
water (10 mL) was added, and stirring was continued for
another 15 min, while warming to 258C. The mixture was
extracted with ether, and the organic phase was washed with
brine, dried (Na2SO4) and evaporated. Flash chroma-
tography (silica, hexanes/EtOAc mixtures) yielded the
intermediate vinylstannane, which was dissolved in
CH2Cl2 (5 mL). A solution of iodine (1.05 equiv.) in
CH2Cl2 (40 mL per g I2) was then added dropwise to this
solution at 08C. After the last few drops, the color of I2
persisted, and the reaction was allowed to continue for
another 5 min at 08C. Then the solvent was evaporated and
the residue was dissolved in ether. KF (1 M solution in
water, 3 equiv.) and Na2S2O3 (sat., 10 mL per mmol
substrate) were added, and the mixture was stirred
for 15 min at 258C during which time a white precipitate
formed. The mixture was filtered through celite, and
the organic phase was dried (Na2SO4) and evaporated.
The residue was purified by flash chromatography
(silica, hexanes/EtOAc mixtures) to yield the desired vinyl
iodide.
1035, 964, 863, 723, 562 cm21 1H NMR (600 MHz,
;
CDCl3) d 2.70 (s, 3H, CH3S), 2.99 (d, J¼1.5 Hz, 3H,
CH3C(I)vC), 6.93 (s, 1H, ArH), 7.08 (q, J¼1.5 Hz, 1H,
HCvC); 13C NMR (150 MHz, CDCl3) d 16.5, 30.7, 101.6,
116.6, 132.6, 152.9, 165.9; MALDI-FTMS m/z 297.9215
(MHþ), calcd for C7H9INS2 297.9216.
4.4.12. Vinyl iodide 20f. Yellow solid (80%). TLC Rf¼
0.19 (silica, hexanes/EtOAc 40:1); IR (film) nmax 2919,
1619, 1567, 1467, 1431, 1373, 1108, 1067, 1014, 961, 867,
1
820, 521 cm21; H NMR (400 MHz, CDCl3) d 2.50 (s,
3H, SCH3), 2.97 (d, J¼1.5 Hz, 3H, CH3C(I)¼C), 7.00 (d,
J¼8.2 Hz, 1H, ArH), 7.18 (q, J¼1.5 Hz, 1H, HCvC), 7.49
(dd, J¼2.6, 8.2 Hz, 1H, ArH), 8.45 (d, J¼2.6 Hz, 1H,
ArH); 13C NMR (100 MHz, CDCl3) d 15.6, 30.5,
104.8, 123.6, 133.4, 134.2, 138.8, 147.0, 152.6;
MALDI-FTMS m/z 291.9655 (MHþ), calcd for C9H11INS
291.9651.
4.4.13. Vinyl iodide 20g. Yellow oil (83%). TLC Rf¼0.28
(silica, hexanes/EtOAc 40:1); IR (film) nmax 2919, 1620,
1549, 1425, 1155, 1138, 1061, 991, 961, 861, 785, 732,
;
550 cm21 1H NMR (400 MHz, CDCl3) d 2.54 (s, 3H,
SCH3), 3.08 (d, J¼1.5 Hz, 3H, CH3C(I)vC), 6.75 (d, J¼
7.6 Hz, 1H, ArH), 7.04 (d, J¼8.2 Hz, 1H, ArH), (q, J¼
1.5 Hz, 1H, HCvC), 7.43 (dd, J¼7.6, 8.2 Hz, 1H, ArH);
13C NMR (100 MHz, CDCl3) d 13.3, 31.2, 105.6, 119.6,

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6425
119.7, 136.0, 139.1, 155.6, 159.4; MALDI-FTMS m/z
291.9653 (MHþ), calcd for C9H11INS 291.9651.
inseparable from 4-tert-butyl pyridine, and was subjected to
the TBAF deprotection conditions (vide infra) as a crude
mixture.
4.5. Synthesis of epothilone analogues 8–14
4.5.5. Product from 20e and 32. Yellow glass (78%, ca. 1:1
mixture of C15 epimers). TLC Rf¼0.40 (silica, hexanes/
EtOAc 5:1); [a]D22¼228 (c 2.0, CHCl3); IR (film) nmax
3416 (br), 2929, 2856, 1732, 1694, 1472, 1251, 1037, 988,
4.5.1. Nozaki–Hiyama–Kishi coupling of aldehydes (32,
40) with vinyl stannanes (20a–g) (general procedure). To
a briefly vacuum-degassed solution of aldehyde 32 (107 mg,
0.15 mmol), the requisite vinyl iodide 20 (0.45 mmol), and
4-tert-butylpyridine (665 mL, 4.5 mmol) in DMSO (3 mL)
were added anhydrous CrCl2 (184 mg, 1.5 mmol) and
anhydrous NiCl2 (4 mg, 0.03 mmol). The mixture was
stirred at 258C for 3 h, after which another portion of vinyl
iodide (0.45 mmol) was added, and stirring was continued
for a further 3 h. This was repeated one more time, after
which stirring was continued overnight. The reaction was
then quenched with water (5 mL), pyridine (1 mL) was
added to prevent Cr-product complexes from being
extracted into the water phase, and the mixture was
extracted with EtOAc (3£25 mL). The combined extract
was washed with brine (2£100 mL), dried (Na2SO4) and
evaporated. Flash chromatography (silica, hexanes/EtOAc
mixtures) yielded the coupling product, in most cases
inseparable from excess 4-tert-butylpyridine.
1
836, 776 cm21; H NMR (600 MHz, CDCl3, total integral
normalized to 85H) d 20.09 to 20.06 (m, 0.5H, c-propyl
CH2), 20.03 to 0.00 (m, 0.5H, c-propyl CH2), 0.01–0.06
(m, 18H, SiCH3), 0.10 (s, 3H, SiCH3), 0.40 (dd, J¼4.0,
8.3 Hz, 0.5H, c-propyl CH2), 0.45 (dd, J¼3.9, 8.3 Hz, 0.5H,
c-propyl CH2), 0.53–0.59 (m, 1H, c-propyl CH), 0.86–0.91
(m, 21H, SiC(CH3)3, CH2CHCH3), 0.95–0.99 (m, 2H,
CH2TMS), 1.01–1.10 (m, 12H, 2£CH3, C(O)CHCH3,
CH2), 1.15–1.21 (m, 1H, CH2), 1.22 (s, 3H, CH3), 1.28–
1.35 (m, 2H, CH2CHCH3, CH2), 1.39–1.44 (m, 1H, CH2),
1.44–1.54 (m, 1H, CH2CHOH), 1.72–1.81 (m, 1H, CH2-
CHOH), 1.87 (br s, 0.5H, OH), 1.97 (br s, 0.5H, OH), 2.08
(s, 3H, HCvCCH3), 2.23 (dd, J¼6.6, 16.2 Hz, 1H,
CH2CO2), 2.42 (dd, J¼3.1, 16.2 Hz, 1H, CH2CO2), 2.70
(s, 3H, SCH3), 3.11–3.16 (m, 1H, C(O)CHCH3), 3.73–3.77
(m, 1H, C(O)CH(CH3)CHOTBS), 4.11–4.20 (m, 2H,
OCH2CH2TMS), 4.20–4.23 (m, 1H, CHOH), 4.37 (dd,
J¼3.1, 6.6 Hz, 1H, CH(OTBS)CH2CO2), 6.49 (s, 0.5H,
CvCH), 6.50 (s, 0.5H, CvCH), 6.94 (s, 0.5H, ArH), 6.95
(s, 0.5H, ArH); 13C NMR (150 MHz, CDCl3, more than one
set of peaks counted due to the presence of C15 epimers) d
24.7, 24.5, 23.8, 23.7, 21.6, 14.2, 14.3, 15.4, 16.5,
17.2, 17.4, 17.5, 17.7, 18.1, 18.5, 18.8, 18.9, 19.1, 19.4,
19.6, 20.3, 20.4, 23.5, 24.8, 26.0, 26.2, 31.0, 35.1, 35.4,
38.9, 40.4, 42.0, 45.1, 53.3, 62.6, 73.8, 77.5, 77.6, 78.3,
78.5, 115.2, 118.1, 118.5, 142.3, 142.4, 153.4, 153.5, 164.9,
172.1, 217.8; MALDI-FTMS m/z 906.5021 (MNaþ), calcd
for C45H85NO6S2Si3Na 906.5018.
4.5.2. Product from 20a and 32. Yellow oil (85% as a ca.
1:1 mixture of C15 epimers). TLC Rf¼0.26 (silica,
hexanes/EtOAc 4:1); [a]2D2¼225 (c 0.36, CH2Cl2); IR
(film) nmax 2943, 2860, 1731, 1696, 1467, 1384, 1290, 1249,
1173, 1079, 985, 832, 773 cm21 1H NMR (500 MHz,
;
CDCl3, total integral normalized to 83H) d 20.11 to 20.01
(m, 1H, c-propyl CH), 20.01 to 0.06, (m, 18H, CH3Si), 0.09
(s, 3H, CH3Si), 0.37–0.41 (dd, J¼4.1, 8.5 Hz, 0.5H,
c-propyl CH2), 0.42–0.46 (dd, J¼4.1, 8.5 Hz, 0.5H,
c-propyl CH2), 0.51–0.59 (m, 1H, c-propyl CH2), 0.83–
0.93 (m, 21H, (CH3)3CSi, CH2CHCH3), 0.96 (t,
J¼8.5 Hz, 2H, CH2CH2TMS), 0.96–1.07 (m, 9H, CH3,
C(O)CHCH3), 1.16–1.44 (m, 6H, C(8)H, C(9)HaHb, and
C(10)H2C(11)H2), 1.21 (s, 3H, C(12)CH3), 1.45–1.53 (m,
1H, C(14)HaHb), 1.56–1.67 (m, 1H, C(9)HaHb), 1.72–1.80
(m, 1H, C(14)HaHb), 2.02 (s, 3H, CH3), 2.22 (dd, J¼6.6,
16.3 Hz, 1H, C(2)HaHb), 2.41 (dd, J¼3.1, 16.3 Hz, 1H,
C(2)HaHb), 2.69 (s, 3H, CH3), 3.08–3.16 (m, 1H,
C(6)H), 3.71–3.77 (m, 1H, C(7)H), 4.08–4.16 (m, 2H,
CH2CH2TMS), 4.18–4.24 (m, 1H, C(15)H), 4.36 (dd,
J¼3.1, 6.6 Hz, C(3)H), 6.55 (s, 0.5H, vinyl H), 6.56
(s, 0.5H, vinyl H), 6.92 (s, 1H, ArH); 13C NMR (125 MHz,
CDCl3, more than 44 peaks counted due to the presence of
two C15 epimers.) d 24.7, 24.5, 23.8, 23.7, 21.6, 13.6,
14.2, 15.4, 17.2, 17.4, 17.5, 17.6, 18.2, 18.5, 18.9, 19.0,
19.1, 19.2, 19.4, 19.6, 20.3, 20.5, 22.6, 23.4, 23.5, 24.8,
26.0, 26.2, 26.8, 27.8, 31.0, 31.1, 31.5, 35.1, 35.4, 38.9,
40.4, 42.0, 42.1, 45.1, 62.7, 73.9, 77.5, 77.6, 78.3, 78.5,
115.3, 115.4, 118.9, 119.2, 142.1, 142.2, 152.8, 152.9,
164.6, 172.2, 217.8; MALDI-FTMS m/z 860.5128 (MNaþ),
calcd for C44H83NO6SSi3Na 860.5141.
4.5.6. Product from 20f and 32. This coupling product was
inseparable from 4-tert-butyl pyridine, and was subjected to
the TBAF deprotection conditions (vide infra) as a crude
mixture.
4.5.7. Product from 20g and 32. This coupling product was
inseparable from 4-tert-butyl pyridine, and was subjected to
the TBAF deprotection conditions (vide infra) as a crude
mixture.
4.5.8. Product from 20c and 40. Yellow glass (87%, ca. 1:1
mixture of C15 epimers). TLC Rf¼0.15 (silica, hexanes/
EtOAc 4:1); [a ]D22¼223 (c 0.19, CH2Cl2); IR (film) nmax
2931, 2861, 1731, 1690, 1467, 1384, 1355, 1249, 1167,
1061, 985, 832, 773, 703 cm21 1H NMR (500 MHz,
;
CDCl3) d 0.02–0.08 (m, 18H, CH3Si), 0.11 (s, 3H,
CH3Si), 0.22–0.34 (m, 2H, c-propyl CH2), 0.44–0.60 (m,
2H, C(12)H, C(13)H), 0.83–0.93 (m, 21H, (CH3)3CSi,
C(8)CH3), 0.98 (t, J¼ 8.6 Hz, 2H, CH2CH2TMS), 1.04 (d,
J¼6.6 Hz, 3H, C(6)CH3), 1.07 (s, 3H, C(4)CaH3CbH3),
1.10–1.42 (m, 7H, C(8)H, C(9)H2, C(10)H2, C(11)H2), 1.23
(s, 3H, C(4)CaH3CbH3), 1.44–1.54 (m, 1H, C(14)HaHb),
1.62–1.73 (m, 1H, C(14)HaHb), 2.0 (s, 3H, vinyl CH3), 2.24
(dd, J¼6.6, 16.2 Hz, 1H, C(2)HaHb), 2.43 (dd, J¼3.3,
16.2 Hz, 1H, C(2)HaHb), 3.10–3.18 (m, 1H, C(6)H), 3.75–
3.79 (m, 1H, C(7)H), 4.09–4.17 (m, 2H, CH2CH2TMS),
4.5.3. Product from 20b and 32. This coupling product was
inseparable from 4-tert-butyl pyridine, and was subjected to
the TBAF deprotection conditions (vide infra) as a crude
mixture.
4.5.4. Product from 20d and 32. This coupling product was

6426
K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
4.19 (s, 2H, ArCH2O), 4.26–4.31 (m, 1H, C(15)H), 4.39
(dd, J¼3.3, 6.6 Hz, C(3)H), 6.60 (s, br 1H, vinyl H), 7.20–
7.28 (m, 4H, ArH), 7.32 (t, J¼7.4 Hz, 6H, ArH), 7.50 (d,
J¼7.4 Hz, 6H, ArH), 7.65 (d, J¼8.1 Hz, 1H, ArH), 8.58 (s,
1H, ArH); 13C NMR (125 MHz, CDCl3, more than one set
of peaks counted due to the presence of two C15 epimers.) d
24.7, 24.5, 23.8, 23.7, 21.6, 11.3, 11.9, 13.9, 14.0, 15.3,
15.5, 17.2, 17.7, 18.2, 18.3, 18.5, 18.9, 19.5, 23.5, 26.0, 26.2,
27.7, 29.7, 30.5, 30.7, 34.8, 38.9, 39.9, 40.4, 45.1, 53.4, 62.7,
63.5, 73.8, 77.6, 78.1, 78.3, 87.2, 123.7, 124.5, 124.6, 127.1,
127.9, 128.6, 131.7, 134.9, 143.8, 144.7, 144.9, 148.0, 155.7,
172.2, 217.9; MALDI-FTMS m/z 1112.6634 (MNaþ), calcd
for C65H99NO7Si3Na 1112.6621.
4.5.12. Hydroxy acid 41b. Yellow solid (57%, ca. 1:1
mixture of C15 epimers). TLC Rf¼0.19 (silica, hexanes/
EtOAc 2:1); [a ]D22¼26 (c 1.0, CHCl3); IR (film) nmax 3369
(br), 2930, 2857, 1783, 1694, 1471, 1251, 1085, 1084, 988,
1
836, 775 cm21; H NMR (500 MHz, CDCl3, total integral
normalized to 75H) d 20.07 (0.5H, c-propyl CH2), 20.03
(0.5H, c-propyl CH2), 0.02–0.11 (m, 12H, SiCH3), 0.43 (dd,
J¼4.0, 8.4 Hz, 0.5H, c-propyl CH2), 0.48 (dd, J¼4.1,
8.5 Hz, 0.5H, c-propyl CH2), 0.54–0.63 (m, 1H, c-propyl
CH), 0.83–0.91 (m, 21H, SiC(CH3)3, CH2CHCH3), 1.00–
1.06 (m, 6H, CH3, C(O)CHCH3), 1.10 (s, 3H, CH3), 1.17–
1.22 (m, 5H, CH2, CH3), 1.25–1.46 (m, 5H, CH2CHCH3,
CH2), 1.52–1.60 (m, 1H, CH2CHOH), 1.73–1.81 (m, 1H,
CH2CHOH), 1.97 (s, 1.5H, HCvCCH3), 1.98 (s, 1.5H,
HCvCCH3), 2.23–2.30 (m, 1H, CH2CO2H), 2.32 (s, 3H,
ArCH3), 2.41–2.52 (m, 1H, CH2CO2H), 3.10–3.17 (m, 1H,
C(O)CHCH3), 3.76–3.81 (m, 1H, C(O)CH(CH3)-
CHOTBS), 4.23–4.28 (m, 1H, CHOH), 4.37–4.41 (m,
1H, CH(OTBS)CH2CO2H), 6.61 (s, 1H, CvCH), 7.20 (d,
J¼8.0 Hz, 1H, ArH), 7.48 (d, J¼8.0 Hz, 1H, ArH), 8.44 (s,
1H, ArH); 13C NMR (125 MHz, CDCl3, more than one set
of peaks counted due to the presence of C15 epimers) d
24.8, 24.7, 24.1, 23.9, 23.8, 23.7, 13.6, 13.7, 14.2,
15.8, 17.4, 17.5, 17.6, 17.7, 18.2, 18.4, 18.9, 19.0, 19.3,
20.0, 20.2, 20.3, 20.4, 20.5, 21.0, 23.3, 23.4, 24.8, 25.3,
26.0, 26.2, 31.1, 34.9, 35.0, 38.9, 39.0, 40.8, 40.9, 41.8,
41.9, 15.0, 45.1, 51.0, 53.5, 60.4, 74.1, 74.2, 74.3, 77.3,
77.4, 78.3, 78.4, 123.6, 123.7, 124.2, 124.7, 130.8, 130.9,
137.1, 144.3, 144.4, 148.7, 148.8, 153.3, 153.4, 175.5,
175.6, 217.8, 218.0; MALDI-FTMS m/z 768.5028 (MNaþ),
calcd for C42H75NO6Si2Na 768.5025.
4.5.9. Product from 20e and 40. Colorless glass (59%, ca.
1:1 mixture of C15 epimers). TLC Rf¼0.27 (silica,
hexanes/EtOAc 5:1); [a ]2D2¼228 (c 2.0, CHCl3); IR
(film) nmax 3396 (br), 2928, 2855, 1734, 1693, 1472,
1251, 1037, 988, 836, 775 cm21 1H NMR (600 MHz,
;
CDCl3, total integral normalized to 83H) d 20.06 to 20.02
(m, 18H, SiCH3), 0.10 (s, 3H, SiCH3), 0.20–0.31 (m, 2H,
c-propyl CH2), 0.42–0.54 (m, 2H, c-propyl CH), 0.87 (s, 9H,
SiC(CH3)3), 0.88–0.91 (m, 12H, SiC(CH3)3, CH2CHCH3),
0.96–0.99 (t, J¼8.6 Hz, 2H, CH2TMS), 1.04 (d, J¼6.8 Hz,
3H, C(O)CHCH3), 1.06 (s, 3H, CH3), 1.09–1.22 (m, 3H,
CH2), 1.23 (s, 3H, CH3), 1.28–1.41 (m, 3H, CH2CHCH3,
CH2), 1.43–1.51 (m, 2H, CH2, CH2CHOH), 1.57–1.62 (m,
1H, CH2CHOH), 1.69 (br s, 0.5H, OH), 1.85 (br s, 0.5H,
OH), 2.07 (s, 3H, HCvCCH3), 2.24 (dd, J¼6.8, 16.4 Hz,
1H, CH2CO2), 2.42 (dd, J¼3.1, 16.4 Hz, 1H, CH2CO2),
2.71 (s, 3H, SCH3), 3.10–3.17 (m, 1H, C(O)CHCH3), 3.75–
3.78 (m, 1H, C(O)CH(CH3)CHOTBS), 4.10–4.19 (m, 2H,
OCH2CH2TMS), 4.20–4.23 (t, J¼6.4 Hz, 1H, CHOH),
4.37 (m, 1H, CH(OTBS)CH2CO2), 6.50 (s, 0.5H, CvCH),
6.51 (s, 0.5H, CvCH), 6.95 (s, 0.5H, ArH), 6.96 (s, 0.5H,
ArH); 13C NMR (150 MHz, CDCl3, more than one set of
peaks counted due to the presence of C15 epimers) d 24.7,
24.4, 23.7, 23.6, 21.6, 11.3, 11.8, 14.2, 14.3, 15.2, 15.3,
15.5, 16.6, 17.2, 17.6, 17.7, 18.2, 18.3, 18.5, 18.9, 19.5, 23.5,
26.0, 26.2, 27.7, 30.7, 34.7, 34.8, 38.8, 39.8, 39.9, 40.4, 45.1,
53.4, 62.7, 73.8, 77.6, 78.1, 78.3, 115.3, 118.2, 118.3, 142.2,
142.4, 153.5, 165.0, 172.2, 217.9; MALDI-FTMS m/z
892.4861 (MNaþ), calcd for C44H83NO6S2Si3Na 892.4862.
4.5.13. Hydroxy acid 41d. Yellow glass (49% for two steps
from aldehyde 32 as a ca. 1:1 mixture of C15 epimers). TLC
Rf¼0.20 (silica, hexanes/EtOAc 1:1); [a]2D2¼þ1 (c 0.19,
CH2Cl2); IR (film) nmax 2933, 2858, 1694, 1600, 1563,
1463, 1382, 1357, 1251, 1145, 1096, 1046, 989, 834, 772,
666 cm21; 1H NMR (500 MHz, CDCl3, normalized to 79H)
d 20.08 to 20.05 (m, 0.5H, c-propyl CH2), 20.05 to
20.02 (m, 0.5H, c-propyl CH2), 0.02–0.14 (m, 12H,
CH3Si), 0.45–0.49 (m, 0.5H, c-propyl CH2), 0.49–0.53 (m,
0.5H, c-propyl CH2), 0.55–0.59 (m, 0.5H, C(13)H),
0.59–0.66 (m, 0.5H, C(13)H), 0.80–0.95 (m, 21H,
(CH3)3CSi, C(8)CH3), 1.00–1.09 (m, 8H, CH2, C(6)CH3,
C(4)CaH3CbH3), 1.14–1.34 (m, 9H, C(4)CaH3CbH3,
C(12)H, CH2), 1.35–1.46 (m, 2H, CH2), 1.52–1.66 (m,
1H, C(14)HaHb), 1.73–1.81 (m, 1H, C(14)HaHb), 1.97 (s,
1.5H, vinyl CH3), 1.99 (s, 1.5H, vinyl CH3), 2.29–2.32 (m,
0.5H, C(2)HaHb), 2.33–2.36 (m, 0.5H, C(2)HaHb), 2.48–
2.58 (m, 1H, C(2)HaHb), 3.07–3.14 (m, 1H, C(6)H), 3.41 (s,
3H, OCH3), 3.80–3.88 (m, 1H, C(7)H), 4.26–4.32 (m, 1H,
C(15)H), 4.37–4.42 (m, 1H, C(3)H), 4.61 (s, 2H, PyCH2O),
4.72 (s, 2H, OCH2O), 6.69 (s, 1H, vinyl H), 7.31–7.35 (m,
2H, ArH), 7.72 (d, J¼7.7 Hz, 1H, ArH), 8.60 (s, 1.5H,
ArH), 8.62 (s, 1.5H, ArH); 13C NMR (125 MHz, CDCl3,
more than one set of peaks counted due to the presence of
two C15 epimers. C(7) obscure under the chloroform
peaks.) d 24.7, 24.8, 24.1, 24.0, 23.9, 23.8, 13.7,
13.8, 13.9, 16.3, 17.0, 17.1, 17.7, 18.2, 18.4, 18.8, 18.9,
19.0, 19.1, 19.7, 20.0, 20.2, 20.5, 23.9, 24.7, 26.0,
26.2, 29.7, 31.3, 33.0, 34.7, 34.8, 38.9, 39.1, 40.6, 40.7,
41.4, 41.7, 44.9, 45.0, 47.2, 53.6, 53.7, 66.0, 66.4,
73.6, 73.9, 78.2, 95.9, 123.8, 123.9, 124.1, 124.6,
4.5.10. TBAF deprotection (general procedure). The
product mixture from the Nozaki–Hiyama–Kishi coupling
was dissolved in THF (1.5 mL), and TBAF (1 M in THF,
0.30 mL, 0.30 mmol) was added at 08C. After 1 h at
08C, another portion of TBAF (0.30 mL, 0.30 mmol) was
added, and the mixture was stirred at 258C for 1 h.
The reaction was quenched with NH4Cl (sat., 5 mL), and
the mixture was extracted with EtOAc (4£20 mL). The
combined extract was dried (Na2SO4) and evaporated, and
the residue was purified by flash chromatography (silica,
hexanes/EtOAc mixtures) to yield the desired hydroxy acid
as a ca. 1:1 mixture of C15 epimers (inseparable at this
stage).
4.5.11. Hydroxy acid 41a. The reaction mixture from the
deprotection was quickly filtered through a plug of silica
gel, and this crude product (73% yield from aldehyde 32)
was subjected to the Yamaguchi macrolactonization (vide
infra) without further purification.

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6427
131.2, 136.4, 145.2, 145.3, 147.7, 147.9, 155.6, 217.9,
218.1; MALDI-FTMS m/z 806.5437 (MHþ), calcd for
C44H80NO8Si2 806.5417.
146.6, 153.0, 153.1, 175.8, 218.0, 218.1; MALDI-FTMS
m/z 800.4754 (MNaþ), calcd for C42H75NO6SSi2Na
800.4746.
4.5.14. Hydroxy acid 41e. Yellow solid (79%, ca. 1:1
mixture of C15 epimers). TLC Rf¼0.37 (silica, hexanes/
EtOAc 2:1); [a ]D22¼223 (c 2.3, CHCl3); IR (film) nmax
3356 (br), 2929, 2856, 1712, 1472, 1253, 1085, 1038, 988,
4.5.16. Hydroxy acid 41g. Yellow glass (46% for two steps
from aldehyde 32 as a ca. 1:1 mixture of C15 epimers). TLC
Rf¼0.46 (silica, hexanes/EtOAc 2:1); [a]2D2¼211 (c 0.19,
CH2Cl2); IR (film) nmax 2933, 2858, 1706, 1557, 1463,
1426, 1364, 1251, 1083, 989, 834, 772, 666 cm21; 1H NMR
(400 MHz, CDCl3, total integral normalized to 75H) d
20.06 (m, 0.5H, c-propyl CH2), 0.00 (m, 0.5H, c-propyl
CH2), 0.03–0.10 (m, 12H, SiCH3), 0.42 (dd, J¼4.0, 8.4 Hz,
0.5H, c-propyl CH2), 0.46 (dd, J¼4.3, 8.3 Hz, 0.5H,
c-propyl CH2), 0.55–0.63 (m, 1H, c-propyl CH), 0.85–
0.91 (m, 21H, SiC(CH3)3, CH2CHCH3), 1.01–1.10 (m,
12H, 2£CH3, C(O)CHCH3, CH2), 1.21 (s, 1.5H, CH3), 1.22
(s, 1.5H, CH3), 1.25–1.45 (m, 5H, CH2CHCH3, CH2),
1.46–1.61 (m, 2H, CH2, CH2CHOH), 1.72–1.83 (m, 1H,
CH2CHOH), 2.17 (s, 3H, HCvCCH3), 2.27 (dd, J¼6.3,
16.6 Hz, 1H, CH2CO2H), 2.43–2.50 (m, 1H, CH2CO2H),
2.57 (s, 3H, SCH3), 3.10–3.17 (m, 1H, C(O)CHCH3), 3.73–
3.78 (m, 1H, C(O)CH(CH3)CHOTBS), 4.20–4.26 (m, 1H,
CHOH), 4.35–4.40 (m, 1H, CH(OTBS)CH2CO2H), 6.48 (s,
0.5H, CvCH), 6.50 (s, 0.5H, CvCH), 6.85–6.89 (m, 1H,
ArH), 6.98 (d, J¼7.9 Hz, 1H, ArH), 7.41 (t, J¼7.9 Hz, 1H,
ArH); 13C NMR (125 MHz, CDCl3, more than one set of
peaks counted due to the presence of C15 epimers) d 24.7,
24.3, 23.8, 23.7, 13.3, 13.7, 14.6, 14.8, 15.6, 15.7, 17.5,
17.6, 17.7, 18.2, 18.5, 18.6, 19.1, 19.5, 20.2, 20.3, 20.4,
23.4, 24.8, 25.2, 26.0, 26.2, 29.7, 30.4, 30.9, 35.1, 35.4,
38.9, 40.3, 41.9, 42.0, 45.2, 51.0, 53.5, 73.7, 77.6, 78.5,
78.6, 118.7, 118.8, 119.9, 120.0, 123.9, 124.4, 135.8, 145.4,
156.5, 156.6, 158.9, 176.4, 218.1; MALDI-FTMS m/z
800.4746 (MNaþ), calcd for C42H75NO6SSi2Na 800.4746.
1
836, 776 cm21; H NMR (600 MHz, CDCl3, total integral
normalized to 73H) d 20.09 to 20.06 (m, 0.5H, c-propyl
CH2), 20.03–0.00 (m, 0.5H, c-propyl CH2), 0.05 (s, 9H,
SiCH3), 0.09 (s, 3H, SiCH3), 0.40 (dd, J¼4.0, 8.3 Hz, 0.5H,
c-propyl CH2), 0.45 (dd, J¼4.2, 8.6 Hz, 0.5H, c-propyl
CH2), 0.53–0.59 (m, 1H, c-propyl CH), 0.85–0.92 (m, 21H,
SiC(CH3)3, CH2CHCH3), 1.00–1.10 (m, 12H, 2£CH3,
C(O)CHCH3, CH2), 1.15–1.20 (m, 1H, CH2), 1.21 (s, 3H,
CH3), 1.27–1.34 (m, 2H, CH2CHCH3, CH2), 1.37–1.44 (m,
1H, CH2), 1.44–1.54 (m, 1H, CH2CHOH), 1.72–1.79 (m,
1H, CH2CHOH), 2.07 (s, 3H, HCvCCH3), 2.30 (dd, J¼
6.8, 16.4 Hz, 1H, CH2CO2H), 2.46–2.51 (m, 1H,
CH2CO2H), 2.69 (s, 3H, SCH3), 3.10–3.15 (m, 1H,
C(O)CHCH3), 3.75–3.79 (m, 1H, C(O)CH(CH3)-
CHOTBS), 4.20–4.24 (m, 1H, CHOH), 4.36–4.39 (m,
1H, CH(OTBS)CH2CO2H), 6.50 (s, 0.5H, CvCH), 6.51 (s,
0.5H, CvCH), 6.94 (s, 0.5H, ArH), 6.95 (s, 0.5H, ArH); 13C
NMR (150 MHz, CDCl3, more than one set of peaks
counted due to the presence of C15 epimers) d 24.6, 24.3,
23.8, 23.7, 14.2, 14.3, 15.6, 15.7, 16.6, 17.5, 17.6, 17.7,
18.1, 18.5, 18.8, 18.9, 19.1, 19.4, 20.2, 20.4, 23.6, 24.8,
26.0, 26.2, 30.9, 31.0, 35.1, 35.3, 38.8, 38.9, 40.0, 41.9,
42.0, 45.1, 53.4, 73.4, 77.5, 78.3, 78.5, 115.2, 118.2, 118.6,
142.3, 153.4, 153.5, 165.1, 177.2, 218.1; MALDI-FTMS
m/z 806.4282 (MNaþ), calcd for C40H73NO6S2Si2Na
806.4315.
4.5.15. Hydroxy acid 41f. Colorless glass (63% from 32,
ca. 1:1 mixture of C15 epimers). TLC Rf¼0.21 (silica,
hexanes/ EtOAc 2:1); [a ]2D2¼23 (c 0.44, CH2Cl2); IR
(film) nmax 2933, 2858, 1693, 1467, 1253, 1086, 984, 833,
4.5.17. Hydroxy acid 42c. The reaction mixture from the
deprotection was quickly filtered through a plug of silica
gel, and this crude product (46% yield from aldehyde 40)
was subjected to the Yamaguchi macrolactonization (vide
infra) without further purification.
774 cm21 1H NMR (500 MHz, CDCl3, total integral
;
normalized to 75H) d 20.08 (m, 0.5H, c-propyl CH2),
20.03 (m, 0.5H, c-propyl CH2), 0.02–0.09 (m, 12H,
SiCH3), 0.42 (dd, J¼4.0, 8.4 Hz, 0.5H, c-propyl CH2), 0.47
(dd, J¼4.0, 8.4 Hz, 0.5H, c-propyl CH2), 0.53–0.60 (m,
1H, c-propyl CH), 0.81–0.90 (m, 21H, SiC(CH3)3, CH2-
CHCH3), 1.00–1.11 (m, 12H, 2 £ CH3, C(O)CHCH3,
CH2), 1.19 (s, 1.5H, CH3), 1.20 (s, 1.5H, CH3), 1.27–1.45
(m, 5H, CH2CHCH3, CH2), 1.47–1.61 (m, 2H, CH2,
CH2CHOH), 1.74–1.81 (m, 1H, CH2CHOH), 2.00 (s, 3H,
HCvCCH3), 2.24–2.32 (m, 1H, CH2CO2H), 2.44–2.49
(m, 1H, CH2CO2H), 2.50 (s, 3H, SCH3), 3.09–3.15 (m,
1H, C(O)CHCH3), 3.75–3.81 (m, 1H, C(O)CH(CH3)-
CHOTBS), 4.21–4.28 (m, 1H, CHOH), 4.35–4.41 (m,
1H, CH(OTBS)CH2CO2H), 6.57 (s, 0.5H, CvCH), 6.58 (s,
0.5H, CvCH), 7.19 (d, J¼8.5 Hz, 1H, ArH), 7.53 (d,
J¼8.5 Hz, 1H, ArH), 8.49 (s, 1H, ArH); 13C NMR
(125 MHz, CDCl3, more than one set of peaks counted
due to the presence of C15 epimers) d 24.7, 24.2, 23.8,
23.7, 13.7, 13.9, 14.0, 15.8, 15.9, 17.5, 17.6, 17.7, 18.2,
18.5, 18.9, 19.0, 19.3, 19.6, 19.8, 20.2, 20.4, 23.5, 23.6,
24.8, 25.1, 26.0, 26.2, 29.7, 30.4, 31.1, 31.5, 35.0, 35.2,
38.9, 39.0, 40.4, 41.8, 41.9, 45.1, 51.0, 53.5, 73.8, 73.9,
78.3, 78.4, 123.7, 124.0, 124.2, 132.7, 132.8, 134.8, 145.0,
4.5.18. Hydroxy acid 42e. Pale yellow glass (66%, ca. 1:1
mixture of C15 epimers). TLC Rf¼0.39 (silica, hexanes/
EtOAc 2:1); [a]D22¼220 (c 1.0, CHCl3); IR (film) nmax
3354 (br), 2928, 2856, 1713, 1471, 1253, 1087, 988, 836,
775 cm21 1H NMR (600 MHz, CDCl3, total integral
;
normalized to 71H) d 0.06–0.08 (m, 9H, SiCH3), 0.10 (s,
3H, SiCH3), 0.20–0.31 (m, 2H, c-propyl CH2), 0.44–0.55
(m, 2H, c-propyl CH), 0.89 (s, 9H, SiC(CH3)3), 0.90–0.93
(m, 12H, SiC(CH3)3, CH2CHCH3), 1.06 (d, J¼6.8 Hz, 3H,
C(O)CHCH3), 1.11 (s, 3H, CH3), 1.16–1.22 (m, 3H, CH2),
1.23 (s, 3H, CH3), 1.30–1.41 (m, 3H, CH2CHCH3, CH2),
1.42–1.63 (m, 3H, CH2CHOH, CH2), 2.06 (s, 3H,
HCvCCH3), 2.32 (dd, J¼6.5, 16.4 Hz, 1H, CH2CO2H),
2.48–2.53 (m, 1H, CH2CO2H), 2.71 (s, 3H, SCH3),
3.12–3.17 (m, 1H, C(O)CHCH3), 3.77–3.80 (m, 1H,
C(O)CH(CH3)CHOTBS), 4.23–4.27 (m, 1H, CHOH),
4.37–4.41 (m, 1H, CH(OTBS)CH2CO2H), 6.53 (s, 0.5H,
CvCH), 6.54 (s, 0.5H, CvCH), 6.95 (s, 0.5H, ArH), 6.96
(s, 0.5H, ArH); 13C NMR (150 MHz, CDCl3, more than one
set of peaks counted due to the presence of C15 epimers) d
23.8, 23.4, 23.3, 22.9, 22.8, 12.1, 12.7, 15.1, 15.2,
16.1, 16.5, 16.6, 17.5, 18.4, 19.0, 19.2, 19.4, 19.7, 19.8,

6428
K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
19.9, 24.6, 26.9, 27.1, 28.5, 31.5, 31.6, 35.5, 35.6, 39.7,
39.8, 40.7, 40.8, 40.9, 45.9, 54.4, 54.5, 74.2, 74.3, 78.3,
78.4, 79.0, 79.1, 116.1, 116.2, 119.2, 119.3, 143.2, 143.3,
154.3, 166.0, 177.4, 177.5, 219.1; MALDI-FTMS m/z
792.4161 (MNaþ), calcd for C39H71NO6S2Si2Na 792.4153.
16.2 Hz, 1H, CH2CO2), 2.73 (dd, J¼5.3, 16.2 Hz, 1H,
CH2CO2), 3.11–3.17 (m, 1H, C(O)CHCH3),
3.79–3.82 (m, 1H, C(O)CH(CH3)CHOTBS), 4.42 (br s,
1H, CH(OTBS)CH2CO2), 5.36 (d, J¼10.5 Hz, 1H,
CH2CO2CH ), 6.53 (s, 1H, CvCH), 7.12 (d, J¼7.9 Hz,
1H, ArH), 7.44 (d, J¼7.9 Hz, 1H, ArH), 8.42 (s, 1H, ArH);
13C NMR (150 MHz, CDCl3) d 24.8, 24.2, 24.1, 23.4,
14.5, 15.8, 17.2, 18.2, 18.3, 18.4, 18.6, 19.1, 19.7,
21.0, 21.5, 21.9, 24.6, 26.0, 26.1, 32.8, 34.9, 39.5,
40.3, 40.8, 44.8, 54.2, 73.7, 76.6, 80.7, 123.9, 125.4,
130.6, 136.5, 140.8, 149.5, 153.5, 170.6, 215.3; MALDI-
FTMS m/z 728.5109 (MHþ), calcd for C42H74NO5Si2
728.5106.
4.5.19. Yamaguchi macrolactonization (general pro-
cedure). To a solution of the hydroxy acid (95 mmol) in
dry THF (8 mL) at 08C was added triethylamine (79 ml,
0.57 mmol) and 2,4,6-trichlorobenzoyl chloride (40 ml,
0.23 mmol). After stirring at 08C for 1 h, the resulting
solution was added over 2 h to a solution of 4-DMAP
(26 mg, 0.21 mmol) in toluene (20 mL) at 758C using a
syringe pump. Stirring was continued at 758C for another
1 h after which the toluene was evaporated under reduced
pressure. The residue was directly subjected to flash
chromatography (silica, hexanes/EtOAc mixtures) to yield
the macrolactone and its (15R )-epimer, readily separable. In
all cases the desired (15S )-epimer eluted after the less polar
(15R )-epimer.
4.5.22. Macrolactone 43d. Yellow glass (35%); TLC
Rf¼0.14 (silica, hexanes/EtOAc 6:1); [a ]2D2¼228 (c 0.12,
CH2Cl2); IR (film) nmax 2931, 2861, 1737, 1690, 1596,
1467, 1378, 1249, 1149, 1102, 1049, 985, 832, 773 cm21
;
1H NMR (600 MHz, CDCl3) d 20.08 to 20.05 (m, 1H,
c-propyl CH2), 0.03–0.10 (m, 9H, CH3Si), 0.11 (s, 3H,
CH3Si), 0.43 (dd, J¼4.4, 8.3 Hz, 1H, c-propyl CH2), 0.61–
0.67 (m, 1H, C(13)H), 0.76–0.82 (m, 1H, C(11)HaHb), 0.84
(s, 9H, (CH3)3CSi), 0.87–0.96 (m, 12H, (CH3)3CSi,
C(8)CH3), 1.07 (s, 3H, C(4)CaH3CbH3), 1.12–1.17 (m,
9H, C(4)CaH3CbH3, C(6)CH3, C(12)CH3), 1.17–1.21 (m,
1H, C(9)HaHb), 1.23–1.32 (m, 1H, C(10)HaHb), 1.38–1.45
(m, 1H, C(9)HaHb), 1.46–1.56 (m, 2H, C(10)HaHb,
C(14)HaHb), 1.57–1.63 (m, 1H, C(8)H), 1.78–1.83 (m,
1H, C(11)HaHb), 2.00–2.08 (m, 1H, C(14)HaHb), 2.11 (s,
3H, vinyl CH3), 2.69 (dd, J¼5.6, 16.2 Hz, 2H, C(2)H2),
3.10–3.15 (m, 1H, C(6)H), 3.40 (s, 3H, OCH3), 3.78–3.81
(m, 1H, C(7)H), 4.45–4.53 (m, 1H, C(3)H), 4.59 (s, 2H,
CH2O), 4.70 (s, 2H, CH2O), 5.35 (br d, J¼10.1 Hz, 1H,
C(15)H), 6.55 (s, 1H, vinyl H), 7.21 (d, J¼7.9 Hz, 1H,
PyH), 7.64 (d, J¼7.9 Hz, 1H, PyH), 8.56 (s, 1H, PyH); 13C
NMR (150 MHz, CDCl3, C(7) is obscure under the chloro-
form peaks) d 24.7, 24.2, 24.1, 23.4, 14.6, 15.9, 17.2,
18.3, 18.4, 18.6, 19.1, 19.7, 21.0, 21.6, 21.9, 24.6, 26.0,
26.1, 32.8, 34.8, 39.5, 40.3, 40.8, 44.9 (br), 54.2, 55.4, 66.6,
73.7, 80.6, 95.8, 124.1, 125.1, 130.7, 135.7, 142.1, 148.7,
155.8, 170.6, 215.3; MALDI-FTMS m/z 810.5116 (MNaþ),
calcd for C44H77NO7Si2Na 810.5130.
4.5.20. Macrolactone 43a. Colorless glass (28% for two
steps from the Nozaki–Hiyama–Kishi coupling product of
aldehyde 32 and vinyl iodide 20a); TLC Rf¼0.21 (silica,
hexanes/EtOAc 20:1); [a]2D2¼233 (c 0.56, CH2Cl2); IR
(film) nmax 2932, 2855, 1739, 1689, 1465, 1383, 1252, 1181,
1153, 1099, 1066, 1017, 984, 869, 836, 776 cm21; 1H NMR
(600 MHz, CDCl3) d 20.10 to 20.08 (m, 1H, c-propyl
CH2), 0.03–0.09 (m, 9H, CH3Si), 0.12 (s, 3H, CH3Si), 0.42
(dd, J¼4.4, 8.3 Hz, 1H, c-propyl CH2), 0.59–0.65 (m, 1H,
C(13)H), 0.73–0.80 (m, 1H, C(11)HaHb), 0.84 (s, 9H,
(CH3)3CSi), 0.92 (m, 12H, (CH3)3CSi, C(8)CH3), 1.06 (s,
3H, C(12)CH3), 1.12–1.19 (m, 10H, C(6)CH3, C(4)(CH3)2,
C(9)HaHb), 1.26–1.32 (m, 1H, C(10)HaHb), 1.46–1.54 (m,
2H, C(10)HaHb, C(14)HaHb), 1.55–1.64 (m, 2H, C(8)H,
C(9)HaHb), 1.78–1.84 (m, 1H, C(11)HaHb), 1.97–2.04 (m,
1H, C(14)HaHb), 2.09 (s, 3H, vinyl CH3), 2.63–2.75 (m,
2H, C(2)H2), 2.70 (s, 3H, thiazole CH3), 3.10–3.15 (m, 1H,
C(6)H), 3.80 (dd, J¼2.2, 4.8 Hz, 1H, C(7)H), 4.48 (br s, 1H,
C(3)H), 5.30–5.35 (m, 1H, C(15)H), 6.53 (s, 1H, vinyl H),
6.94 (s, 1H, ArH); 13C NMR (150 MHz, CDCl3, C(7) is
obscure under chloroform peaks) d 24.8, 24.2, 23.4, 14.9,
15.9, 17.3, 18.4, 18.6, 19.2, 19.8, 21.0, 21.6, 22.0, 24.6,
26.1, 32.8, 34.9, 39.4, 40.2, 40.8, 45.1, 54.1, 73.8, 80.6,
116.2, 119.7, 138.8, 152.5, 164.6, 170.6, 215.3; MALDI-
FTMS m/z 734.4639 (MHþ), calcd for C40H72NO5SSi2
734.4664.
4.5.23. Macrolactone 43e. This product was isolated as
a crude mixture which was directly subjected to the
global desilylation conditions (vide infra) without further
purification.
4.5.21. Macrolactone 43b. Colorless glass (28%); TLC
Rf¼0.27 (silica, hexanes/EtOAc 10:1); [a ]2D2¼228 (c 1.0,
CHCl3); IR (film) nmax 2929, 2856, 1740, 1695, 1472, 1384,
1253, 1100, 1020, 986, 836, 775 cm21; 1H NMR (600 MHz,
CDCl3) d 20.06 (1H, c-propyl CH2), 0.05 (s, 3H, SiCH3),
0.06 (s, 3H, SiCH3), 0.08 (s, 3H, SiCH3), 0.12 (s, 3H,
SiCH3), 0.43 (dd, J¼4.2, 8.6 Hz, 1H, c-propyl CH2), 0.61–
0.67 (m, 1H, c-propyl CH), 0.74–0.82 (m, 1H, CH2), 0.85
(s, 9H, SiC(CH3)3), 0.93 (s, 9H, SiC(CH3)3), 0.95 (d,
J¼6.6 Hz, 3H, CH2CHCH3), 1.07 (s, 3H, CH3), 1.14 (s, 3H,
CH3), 1.14 (d, J¼7.0 Hz, 3H, C(O)CHCH3), 1.16 (s, 3H,
CH3), 1.17–1.34 (m, 3H, CH2), 1.48–1.55 (m, 2H, CO2-
CHCH2, CH2) 1.59–1.63 (m, 1H, CH2CHCH3), 1.79–1.85
(m, 1H, CH2), 2.03–2.09 (m, 1H, CO2CHCH2), 2.11 (s, 3H,
HCvCCH3), 2.32 (s, 3H, ArCH3), 2.66 (dd, J¼5.3,
4.5.24. Macrolactone 43f. Colorless glass (45%); TLC
Rf¼0.20 (silica, hexanes/EtOAc 10:1); [a]2D2¼230 (c
0.10, CH2Cl2); IR (film) nmax 2933, 285, 1737, 1668, 1463,
1382, 1357, 1251, 1102, 1015, 983, 871, 834, 772 cm21; 1H
NMR (600 MHz, CDCl3) d 20.09 to 20.06 (m, 1H,
c-propyl CH2), 0.03–0.09 (m, 9H, CH3Si), 0.11 (s, 3H,
CH3Si), 0.43 (dd, J¼4.4, 8.3 Hz, 1H, c-propyl CH2), 0.60–
0.66 (m, 1H, C(13)H), 0.75–0.82 (m, 1H, C(11)HaHb), 0.84
(s, 9H, (CH3)3CSi), 0.92 (s, 9H, (CH3)3CSi), 0.94 (d,
J¼7.0 Hz, 3H, C(8)CH3), 1.06 (s, 3H, C(12)CH3), 1.12–
1.19 (m, 10H, C(6)CH3, C(4)(CH3)2, C(9)HaHb), 1.26–1.32
(m, 1H, C(10)HaHb), 1.39–1.46 (m, 1H, C(9)HaHb), 1.46–
1.55 (m, 2H, C(10)HaHb, C(14)HaHb), 1.56–1.63 (m, 1H,
C(8)H), 1.77–1.83 (m, 1H, C(11)HaHb), 1.98–2.06 (m, 1H,
C(14)HaHb), 2.11 (s, 3H, vinyl CH3), 2.45 (s, 3H, SCH3),

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6429
2.65 (dd, J¼4.8, 16.2 Hz, 1H, C(2)HaHb), 2.72 (dd, J¼5.7,
16.2 Hz, 1H, C(2)HaHb), 3.09–3.15 (m, 1H, C(6)H), 3.78–
3.81 (m, 1H, C(7)H), 4.48 (br s, 1H, C(3)H), 5.33 (br d,
J¼10.1 Hz, 1H, C(15)H), 6.49 (s, 1H, vinyl H), 7.13 (d,
J¼8.3 Hz, 1H, PyH), 7.51 (d, J¼8.3 Hz, 1H, PyH), 8.48 (s,
1H, PyH); 13C NMR (150 MHz, CDCl3, C(7) is obscure
under chloroform peaks.) d 24.8, 24.2, 24.1, 23.4, 14.7,
15.8, 15.9, 17.2, 18.3, 18.4, 18.6, 19.1, 19.7, 21.0, 21.6,
21.9, 24.6, 26.0, 26.1, 32.8, 34.6, 39.5, 40.3, 40.7, 45.1,
54.1, 73.7, 80.7, 124.2, 124.8, 132.6, 134.3, 141.7, 147.2,
153.1, 170.6, 215.2; MALDI-FTMS m/z 760.4799 (MHþ),
calcd for C42H74NO5SSi2 760.4820.
4.28 (m, 1H, C(3)H), 5.22 (br d, J¼11.0 Hz, 1H, C(15)H),
6.53 (s, 1H, vinyl H), 7.20 (d, J¼7.7 Hz, 1H, PyH), 7.23–
7.28 (m, 3H, ArH), 7.29–7.35 (m, 6H, ArH), 7.47–7.52 (m,
6H, ArH), 7.63 (d, J¼7.7 Hz, 1H, PyH), 8.58 (s, 1H, PyH);
13C NMR (125 MHz, CDCl3) d 24.7, 24.5, 23.8, 23.7,
21.6, 13.6, 14.2, 15.4, 17.2, 17.4, 17.5, 17.6, 18.2, 18.5,
18.9, 19.0, 19.1, 19.2, 19.4, 19.6, 20.3, 20.5, 22.6, 23.4,
23.5, 24.8, 26.0, 26.2, 26.8, 27.8, 31.0, 31.1, 31.5, 35.1,
35.4, 38.9, 40.4, 42.0, 42.1, 45.1, 62.7, 73.9, 77.5, 77.6,
78.3, 78.5, 115.3, 115.4, 118.9, 119.2, 142.1, 142.2, 152.8,
152.9, 164.6, 172.2, 217.8; MALDI-FTMS m/z 972.5969
(MHþ), calcd for C60H86NO6Si2 972.5988.
4.5.25. Macrolactone 43g. Yellow glass (37%); TLC
Rf¼0.47 (silica, hexanes/EtOAc 10:1); [a ]2D2¼214
(c 0.31, CHCl3); IR (film) nmax 2929, 2856, 1740, 1696,
1557, 1461, 1431, 1379, 1250, 1099, 107, 979, 836,
4.5.27. Macrolactone 44e. Colorless glass (47%); TLC
Rf¼0.31 (silica, hexanes/EtOAc 15:1); [a ]2D2¼219 (c
0.50, CHCl3); IR (film) nmax 2929, 2855, 1741, 1697, 1472,
1254, 1102, 1036, 986, 836, 775 cm21; 1H NMR (500 MHz,
CDCl3) d 0.02 (s, 3H, SiCH3), 0.08 (s, 3H, SiCH3), 0.09 (s,
3H, SiCH3), 0.15 (s, 3H, SiCH3), 0.17–0.22 (m, 2H,
c-propyl CH2), 0.43–0.49 (m, 1H, c-propyl CH), 0.66–0.73
(m, 1H, c-propyl CH), 0.78–0.84 (m, 1H, CH2), 0.86 (s, 9H,
SiC(CH3)3), 0.91–0.95 (m, 12H, SiC(CH3)3, CH2CHCH3),
1.13 (d, J¼6.6 Hz, 3H, C(O)CHCH3), 1.16 (s, 3H, CH3),
1.20 (s, 3H, CH3), 1.23–1.36 (m, 2H, CH2), 1.41–1.50 (m,
2H, CO2CHCH2, CH2), 1.57–1.66 (m, 1H, CH2CHCH3),
1.67–1.78 (m, 2H, CH2), 1.80–1.86 (m, 1H, CH2), 2.11 (s,
3H, HCvCCH3), 2.70 (s, 3H, SCH3), 2.73 (dd, J¼7.7,
16.9 Hz, 1H, CH2CO2), 2.85 (dd, J¼3.7, 16.9 Hz, 1H,
CH2CO2), 3.10–3.17 (m, 1H, C(O)CHCH3), 3.88 (d, J¼
7.4 Hz, 1H, C(O)CH(CH3)CHOTBS), 4.22–4.27 (m,
1H, CH(OTBS)CH2CO2), 5.19 (d, J¼10.7 Hz, 1H,
CH2CO2CH ), 6.45 (s, 1H, CvCH), 6.96 (s, 1H, ArH);
13C NMR (125 MHz, CDCl3) d 25.3, 23.9, 23.7, 23.3,
10.8, 14.9, 16.6, 16.9, 17.2, 18.5, 18.57, 18.6, 22.9, 23.2,
26.2, 26.3, 29.7, 31.0, 34.9, 37.6, 39.4, 39.6, 47.0, 53.8,
74.8, 78.5, 80.9, 115.9, 118.7, 139.1, 153.1, 165.0, 170.9,
215.3; MALDI-FTMS m/z 774.4056 (MNaþ), calcd for
C39H69NO5S2Si2Na 774.4048.
774 cm21 1H NMR (500 MHz, CDCl3) d 20.08 to
;
20.04 (m, 1H, c-propyl CH2), 0.02–0.10 (m, 9H, CH3Si),
0.02–0.10 (m, 9H, CH3Si), 0.12 (s, 3H, CH3Si), 0.44 (dd,
J¼4.4, 8.4 Hz, 1H, c-propyl CH2), 0.61–0.68 (m, 1H,
C(13)H), 0.76–0.82 (m, 1H, C(11)HaHb), 0.85 (s, 9H,
(CH3)3CSi), 0.92 (s, 9H, (CH3)3CSi), 0.95 (d, J¼7.0 Hz,
3H, C(8)CH3), 1.07 (s, 3H, C(12)CH3), 1.12–1.18 (m, 9H,
C(6)CH3, C(4)(CH3)2), 1.18–1.23 (m, 1H, C(9)HaHb),
1.24–1.32 (m, 1H, C(10)HaHb), 1.39–1.46 (m, 1H,
C(9)HaHb), 1.46–1.55 (m, 2H, C(10)HaHb, C(14)HaHb),
1.56–1.63 (m, 1H, C(8)H), 1.78–1.84 (m, 1H, C(11)HaHb),
2.00–2.09 (m, 1H, C(14)HaHb), 2.24 (s, 3H, vinyl CH3),
2.57 (s, 3H, SCH3), 2.65 (dd, J¼5.2, 16.2 Hz, 1H,
C(2)HaHb), 2.72 (dd, J¼5.5, 16.2 Hz, 1H, C(2)HaHb),
3.10–3.16 (m, 1H, C(6)H), 3.79–3.82 (m, 1H, C(7)H), 4.51
(br s, 1H, C(3)H), 5.36 (br d, J¼10.3 Hz, 1H, C(15)H), 6.45
(s, 1H, vinyl H), 6.86 (d, J¼8.1 Hz, 1H, PyH), 6.99 (d,
J¼8.1 Hz, 1H, PyH), 7.41 (t, J¼8.1 Hz, 1H, PyH); 13C
NMR (125 MHz, CDCl3, C(7) is obscure under chloroform
peaks.) d 24.7, 24.2, 23.4, 13.3, 15.3, 15.8, 17.1, 18.3,
18.4, 18.6, 19.1, 19.7, 20.6, 21.6, 24.6, 26.0, 26.1, 32.8,
34.8, 39.6, 40.5, 40.6, 44.7, 54.2, 73.6, 80.8, 119.0, 120.3,
124.8, 135.8, 142.2, 156.1, 158.9, 170.6, 215.2; MALDI-
FTMS m/z 760.4802 (MHþ), calcd for C42H74NO5SSi2
760.4820.
4.5.28. Global desilylation (general procedure). The
macrolactone was dissolved in 20% v/v TFA in CH2Cl2,
and the solution was kept at 258C for 3 h, after which the
volatiles were evaporated without heating. The residue was
dissolved in EtOAc, and the solution was washed with
NaHCO3 (sat.), dried (Na2SO4) and evaporated. Flash
chromatography (silica, hexanes/EtOAc mixtures) afforded
the pure epothilone.
4.5.26. Macrolactone 44c. Colorless glass (33% for two
steps from the Nozaki–Hiyama–Kishi coupling product of
aldehyde 40 and vinyl iodide 20c); TLC Rf¼0.46 (silica,
hexanes/EtOAc 10:1); [a ]2D2¼217 (c 0.56, CH2Cl2); IR
(film) nmax 2931, 2861, 1743, 1696, 1467, 1378, 1249, 1161,
1
1073, 1020, 985, 873, 833, 773, 703, 579 cm21; H NMR
4.5.29. Epothilone 6. Colorless glass (73%); TLC Rf¼0.25
(silica, hexanes/EtOAc 2:1); [a ]2D2¼234 (c 0.11, CH2Cl2);
IR (film) nmax 3472 (br), 2931, 1732, 1684, 1456, 1378,
(500 MHz, CDCl3) d 0.02 (s, 3H, CH3Si), 0.09 (m, 6H,
CH3Si), 0.14 (m, 3H, CH3Si), 0.18–0.22 (m, 2H, c-propyl
CH2), 0.45–0.51 (m, 1H, C(13)H), 0.67–0.74 (m, 1H,
C(12)H), 0.78–0.84 (m, 1H, C(11)HaHb), 0.86 (s, 9H,
(CH3)3CSi), 0.91–0.97 (m, 12H, (CH3)3CSi, C(8)CH3),
1.10–1.15 (m, 1H, C(9)HaHb), 1.13 (d, J¼7.0 Hz,
C(6)CH3), 1.16 (s, 3H, C(4)CaH3CbH3), 1.20 (s, 3H,
C(4)CaH3CbH3), 1.30–1.39 (m, 1H, C(9)HaHb), 1.42–1.53
(m, 2H, C(10)HaHb, C(14)HaHb), 1.58–1.66 (m, 1H,
C(8)H), 1.67–1.77 (m, 2H, C(10)HaHb, C(11)HaHb),
1.83–1.90 (m, 1H, C(14)HaHb), 2.12 (s, 3H, CH3), 2.74
(dd, J¼7.7, 16.9 Hz, 1H, C(2)HaHb), 2.86 (dd, J¼3.7,
16.9 Hz, 1H, C(2)HaHb), 3.11–3.17 (m, 1H, C(6)H),
3.86–3.89 (m, 1H, C(7)H), 4.18 (s, 2H, ArCH2O), 4.23–
1258, 1179, 1149, 1067, 1043, 1012, 973, 873, 732 cm21
;
1H NMR (500 MHz, CDCl3, d 20.06 to 20.04 (m, 1H,
c-propyl CH), 0.46–0.50 (m, 1H, c-propyl CH), 0.57–0.63
(m, 1H, C(13)H), 0.67–0.73 (m, 1H, C(9)HaHb), 0.94 (d,
J¼7.0 Hz, 3H, C(8)HCH3), 0.98 (s, 3H, C(4)CaH3), 1.07 (s,
3H, C(4)CbH3), 1.12 (d, J¼7.0 Hz, 3H, C(6)HCH3), 1.25–
1.45 (m, 5H, C(9)HaHb, C(10)H2, C(11)H2), 1.36 (s, 3H,
C(12)CH3), 1.61–1.69 (m, 1H, C(14)HaHb), 1.72–1.80 (m,
1H, C(8)H), 1.87–1.94 (m, 1H, C(14)HaHb), 2.04 (s, 3H,
vinyl CH3), 2.44 (dd, J¼2.6, 15.6 Hz, 1H, C(2)HaHb), 2.54
(dd, J¼10.6, 15.6 Hz, 1H, C(2)HaHb), 2.69 (s, 3H, thiazole
CH3), 3.12 (br s, 1H, OH), 3.22 (br s, 1H, OH), 3.32 (dq,

6430
K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
J¼2.4, 7.0 Hz, 1H, C(6)H), 3.63–3.67 (m, 1H, C(7)H),
4.35 (br d, J¼10.6 Hz, 1H, C(3)H), 5.28–5.33 (m, 1H,
C(15)H), 6.54 (s, 1H, vinyl H), 6.93 (s, 1H, thiazole H); 13C
NMR (125 MHz, CDCl3) d 11.8, 15.3, 15.9, 18.3, 18.5,
19.1, 19.3, 19.8, 20.8, 21.1, 22.5, 32.0, 33.9, 36.3, 39.0,
40.9, 41.5, 53.5, 71.3, 72.6, 79.5, 115.8, 119.0, 138.2, 152.2,
164.7, 170.6, 220.8; MALDI-FTMS m/z 506.2931 (MHþ),
calcd for C28H44NO5S 506.2935.
J¼8.3 Hz, 1H, ArH), 7.66 (1H, ArH), 8.36 (s, 1H, ArH);
13C NMR (150 MHz, CDCl3) d 11.6, 14.9, 16.0, 17.4, 18.4,
19.1, 19.8, 20.8, 21.7, 22.2, 31.9, 33.5, 36.1, 39.3, 40.8,
41.1, 54.0, 62.4, 70.8, 72.3, 78.6, 123.7, 124.0, 133.9, 135.4,
141.2, 147.7, 155.1, 170.5, 221.1; MALDI-FTMS m/z
516.3330 (MHþ), calcd for C30H46NO6 516.3319.
4.5.32. Epothilone 12. Viscous oil (17% from 41e); TLC
Rf¼0.38 (silica, hexanes/EtOAc 2:1); [a ]2D2¼252 (c 0.50,
CHCl3); IR (film) nmax 3490 (br), 2933, 1732, 1686, 1255,
1038, 756 cm21; 1H NMR (600 MHz, CDCl3) d 20.04 (m,
1H, c-propyl CH2), 0.49 (dd, J¼4.2, 8.6 Hz, 1H, c-propyl
CH2), 0.59–0.64 (m, 1H, c-propyl CH), 0.67–0.73 (m, 1H,
CH2), 0.94 (d, J¼7.0 Hz, 3H, CH2CHCH3), 0.99 (s, 3H,
CH3), 1.08 (s, 3H, CH3), 1.12 (d, J¼6.6 Hz, 3H,
C(O)CHCH3), 1.37 (s, 3H, CH3), 1.38–1.46 (m, 3H,
CH2), 1.65–1.71 (m, 1H, CH2), 1.72–1.81 (m, 3H, CH2-
CHCH3, CH2), 1.87–1.93 (m, 1H, CH2), 2.08 (s, 3H,
HCvCCH3), 2.45 (dd, J¼2.6, 15.4 Hz, 1H, CH2CO2), 2.54
(dd, J¼10.5, 15.4 Hz, 1H, CH2CO2), 2.70 (s, 3H, SCH3),
3.15 (br s, 1H, OH), 3.30–3.33 (m, 1H, C(O)CHCH3), 3.66
(dd, J¼2.2, 6.6 Hz, 1H, C(O)CH(CH3)CHOH), 4.34 (dd,
J¼2.6, 10.5 Hz, 1H, CH(OH)CH2CO2), 5.31 (dd, J¼2.9,
8.6 Hz, 1H, CH2CO2CH ), 6.47 (s, 1H, CvCH), 6.96 (s, 1H,
ArH); 13C NMR (150 MHz, CDCl3) d 12.6, 16.2, 16.7, 17.5,
19.2, 19.3, 20.0, 20.8, 21.7, 22.0, 23.3, 32.8, 34.5, 37.0,
39.8, 41.8, 42.4, 54.4, 72.3, 73.3, 80.5, 116.6, 119.4, 127.7,
139.2, 153.7, 166.1, 171.5, 221.6; MALDI-FTMS m/z
538.2666 (MHþ), calcd for C28H44NO5S2 538.2655.
4.5.30. Epothilone 8. Colorless glass (48%); TLC Rf¼0.52
(silica, hexanes/EtOAc 1:1); [a ]2D2¼254 (c 0.30, CHCl3);
IR (film) nmax 3445 (br), 2936, 1732, 1682, 1454, 1383,
1259, 756 cm21; 1H NMR (500 MHz, CDCl3) d 20.03 (m,
1H, c-propyl CH2), 0.49 (dd, J¼4.2, 8.6 Hz, 1H, c-propyl
CH2), 0.60–0.67 (m, 1H, c-propyl CH), 0.68–0.75 (m, 1H,
CH2), 0.90 (d, J¼7.4 Hz, 3H, CH2CHCH3), 1.01 (s, 3H,
CH3), 1.08 (s, 3H, CH3), 1.12 (d, J¼7.0 Hz, 3H,
C(O)CHCH3), 1.37 (s, 3H, CH3), 1.38–1.46 (m, 3H,
CH2), 1.71–1.80 (m, 3H, CH2CHCH3, CH2), 1.86–1.95
(m, 2H, CH2), 2.02 (s, 3H, HCvCCH3), 2.33 (s, 3H,
ArCH3), 2.42 (dd, J¼2.4, 15.4 Hz, 1H, CH2CO2), 2.55 (dd,
J¼10.6, 15.4 Hz, 1H, CH2CO2), 3.24 (br s, 1H, OH), 3.30–
3.34 (m, 1H, C(O)CHCH3), 3.66 (d, J¼6.3 Hz, 1H,
C(O)CH(CH3)CHOH), 3.80 (br s, 1H, OH), 4.42 (m,
1H, CH(OH)CH2CO2), 5.32 (dd, J¼3.3, 8.4 Hz, 1H,
CH2CO2CH ), 6.57 (s, 1H, CvCH), 7.17 (d, J¼8.1 Hz,
1H, ArH), 7.47 (dd, J¼1.9, 7.7 Hz, 1H, ArH), 8.39 (d,
J¼1.9 Hz, 1H, ArH); 13C NMR (125 MHz, CDCl3) d 11.7,
15.1, 15.6, 18.0, 18.2, 18.4, 19.2, 19.7, 20.7, 21.4, 22.4,
32.0, 33.7, 36.3, 39.1, 40.8, 41.3, 53.7, 71.1, 72.5, 79.1,
123.5, 124.6, 130.9, 136.8, 140.1, 149.4, 153.1, 170.5,
221.0; MALDI-FTMS m/z 500.3369 (MHþ), calcd for
C30H46NO5 500.3370.
4.5.33. Epothilone 13. Colorless glass (68%); TLC
Rf¼0.57 (silica, hexanes/EtOAc 1:1); [a]2D2¼246 (c
0.34, CH2Cl2); IR (film) nmax 3484 (br), 2932, 1731,
1684, 1469, 1367, 1255, 1150, 1044, 1009, 973, 879, 826,
1
4.5.31. Epothilone 10. The general procedure failed to
cleave the MOM protecting group cleanly. Therefore, this
group was first removed using bromotrimethylsilane as
follows: To a solution of protected epothilone 43d (11 mg,
732 cm21; H NMR (500 MHz, CDCl3, d 0.03–0.06 (m,
1H, c-propyl CH), 0.55–0.59 (m, 1H, c-propyl CH), 0.67–
0.73 (m, 1H, C(13)H), 0.73–0.81 (m, 1H, C(9)HaHb), 0.98
(d, J¼7.0 Hz, 3H, C(8)HCH3), 1.08 (s, 3H, C(4)CaH3), 1.15
(s, 3H, C(4)CbH3), 1.19 (d, J¼7.0 Hz, 3H, C(6)HCH3),
1.32–1.52 (m, 5H, C(9)HaHb, C(10)H2, C(11)H2), 1.45 (s,
3H, C(12)CH3), 1.76–1.88 (m, 2H, C(8)H, C(14)HaHb),
1.92–2.02 (m, 1H, C(14)HaHb), 2.12 (s, 3H, vinyl CH3),
2.51 (dd, J¼2.6, 15.4 Hz, 1H, C(2)HaHb), 2.59 (s, 3H,
SCH3), 2.62 (dd, J¼10.7, 15.4 Hz, 1H, C(2)HaHb), 3.28 (s,
1H, OH), 3.39 (dq, J¼2.2, 7.0 Hz, 1H, C(6)H), 3.62 (br s,
1H, OH), 3.69–3.76 (m, 1H, C(7)H), 4.47 (dd, J¼2.6,
10.7 Hz, 1H, C(3)H), 5.33–5.43 (m, 1H, C(15)H), 6.61 (s,
1H, vinyl H), 7.26 (d, J¼8.3 Hz, 1H, PyH), 7.61 (d,
J¼8.3 Hz, 1H, PyH), 8.52 (s, 1H, PyH); 13C NMR
(125 MHz, CDCl3) d 11.7, 15.1, 15.7, 15.9, 18.0, 18.4,
19.2, 19.8, 20.8, 21.4, 22.4, 31.9, 33.7, 36.2, 39.1, 40.8,
41.3, 53.7, 71.2, 72.5, 79.3, 123.9, 124.1, 132.9, 134.5,
140.8, 147.1, 152.7, 170.6, 220.9; MALDI-FTMS m/z
554.2915 (MNaþ), calcd for C30H45NO5SNa 554.2910.
˚
14 mmol) in dry CH2Cl2 (0.4 mL) was added powdered 4 A
MS (5 mg), and the resulting mixture was cooled to 2308C.
Bromotrimethylsilane (18.4 mL, 140 mmol) was added
dropwise, and the mixture was stirred at 2308C for 1 h,
after which the reaction was quenched with NaHCO3 (sat.)
and extracted five times with EtOAc. The combined extract
was dried and evaporated, and the residue subjected to the
general desilylation procedure to yield 10 as a colorless
glass (56%); TLC Rf¼0.42 (silica, hexanes/EtOAc 1:4);
[a ]2D2¼252 (c 0.12, CH2Cl2); IR (film) nmax 3401 (br),
2931, 1731, 1684, 1596, 1561, 1461, 1378, 1331, 1290,
1
1255, 1173, 1149, 1044, 1008, 979, 879, 732 cm21; H
NMR (600 MHz, CDCl3) d 20.03 (m, 1H, c-propyl CH2),
0.49 (dd, J¼4.2, 8.6 Hz, 1H, c-propyl CH2), 0.60–0.64 (m,
1H, c-propyl CH), 0.64–0.71 (m, 1H, CH2), 0.87 (d,
J¼7.0 Hz, 3H, CH2CHCH3), 1.00 (s, 3H, CH3), 1.07 (s, 3H,
CH3), 1.11 (d, J¼6.5 Hz, 3H, C(O)CHCH3), 1.38 (s, 3H,
CH3), 1.38–1.44 (m, 3H, CH2), 1.72–1.80 (m, 3H, CH2-
CHCH3, CH2), 1.81–1.89 (m, 2H, CH2), 1.99 (s, 3H,
HCvCCH3), 2.40 (dd, J¼2.2, 15.3 Hz, 1H, CH2CO2), 2.55
(dd, J¼11.0, 15.3 Hz, 1H, CH2CO2), 3.08 (br s, 1H, OH),
3.29–3.33 (m, 1H, C(O)CHCH3), 3.63 (d, J¼6.5 Hz, 1H,
C(O)CH(CH3)CHOH), 4.23 (br s, 1H, OH), 4.45 (m, 1H,
CH(OH)CH2CO2), 4.67 (s, 2H, CH2OH), 5.30 (dd, J¼3.1,
7.9 Hz, 1H, CH2CO2CH ), 6.60 (s, 1H, CvCH), 7.25 (d,
4.5.34. Epothilone 14. Colorless glass (48%); TLC
Rf¼0.42 (silica, hexanes/EtOAc 2:1); [a]2D2¼238 (c
0.20, CH2Cl2); IR (film) nmax 3478 (br), 2930, 1732,
1682, 1556, 1434, 1378, 1257, 1149, 1137, 1067, 1044,
1
1012, 979, 785, 732 cm21; H NMR (600 MHz, CDCl3, d
20.05 to 20.02 (m, 1H, c-propyl CH), 0.48–0.51 (m, 1H,
c-propyl CH), 0.60–0.66 (m, 1H, C(13)H), 0.66–0.72 (m,
1H, C(9)HaHb), 0.89 (d, J¼7.0 Hz, 3H, C(8)HCH3), 1.01 (s,

K. C. Nicolaou et al. / Tetrahedron 58 (2002) 6413–6432
6431
3H, C(4)CaH3), 1.08 (s, 3H, C(4)CbH3), 1.11 (d, J¼7.0 Hz,
3H, C(6)HCH3), 1.27–1.46 (m, 5H, C(9)HaHb, C(10)H2,
C(11)H2), 1.38 (s, 3H, C(12)CH3), 1.71–1.80 (m, 2H,
C(8)H, C(14)HaHb), 1.85–1.93 (m, 1H, C(14)HaHb), 2.15
(s, 3H, vinyl CH3), 2.45 (dd, J¼2.6, 15.4 Hz, 1H,
C(2)HaHb), 2.51–2.58 (dd, J¼10.7, 15.4 Hz, 1H,
C(2)HaHb), 2.56 (s, 3H, SCH3), 3.08 (br d, J¼4.0 Hz, 1H,
OH), 3.16 (s, 1H, OH), 3.28–3.34 (m, 1H, C(6)H), 3.61–
3.69 (m, 1H, C(7)H), 4.32–4.39 (m, 1H, C(3)H), 5.30–5.33
(m, 1H, C(15)H), 6.42 (s, 1H, vinyl H), 6.88 (d, J¼7.4 Hz,
1H, PyH), 6.99 (d, J¼7.9 Hz, 1H, PyH), 7.40–7.47 (m,
1H, PyH); 13C NMR (150 MHz, CDCl3) d 11.7, 13.4, 15.2,
16.0, 18.2, 18.4, 19.1, 20.0, 20.9, 21.2, 22.3, 31.8, 33.5,
36.1, 38.9, 41.0, 41.4, 53.6, 71.4, 72.3, 79.7, 119.0, 120.0,
124.5, 135.9, 140.9, 155.8, 159.1, 170.8, 220.7; MALDI-
FTMS m/z 532.3078 (MHþ), calcd for C30H45NO5S
532.3091.
30.5, 34.5, 35.6, 37.8, 38.8, 43.5, 53.1, 71.8, 75.0, 80.5,
116.0, 119.1, 138.1, 152.7, 165.4, 171.0, 219.1; MALDI-
FTMS m/z 546.2330 (MNaþ), calcd for C27H41NO5S2Na
546.2318.
Acknowledgments
We thank Drs D. H. Huang and G. Siuzdak (TSRI) for NMR
and mass spectrometric assistance, respectively. We would
like to acknowledge the excellent technical assistance of
R. Reute and J. Loretan for KB-31 cytotoxicity and tubulin
polymerization assays, respectively. Financial support for
this work was provided by The Skaggs Institute for
Chemical Biology, the National Institutes of Health
(USA), fellowships from the STINT Scholar Program (to
A. R.), Avon Foundation (to A. O.-B.), McyT grants
BIO2000-0748 (to J. M. A.) and BIO2001-1725 (to J. F. D.),
and grants from Abbott, Amgen, ArrayBiopharma, Boeh-
ringer-Ingelheim, Glaxo, Hoffmann-La Roche, DuPont,
Merck, Novartis, Pfizer, and Schering Plough.
4.5.35. Epothilone 9. Colorless glass (54%); TLC Rf¼0.13
(silica, hexanes/EtOAc 1:2); [a]2D2¼224 (c 0.14, CH2Cl2);
IR (film) nmax 3379, 2920, 2857, 1725, 1688, 1600, 1459,
1
1370, 1255, 1151, 1047, 1010, 979, 880, 734 cm21; H
NMR (500 MHz, CDCl3) d 0.18–0.26 (m, 2H, c-propyl
CH2), 0.47–0.54 (m, 1H, C(13)H), 0.60–0.67 (m, 1H,
C(12)H), 0.70–0.78 (m, 1H, C(11)HaHb), 0.90 (d, J¼
7.0 Hz, 3H, C(8)CH3), 1.10 (s, 3H, C(4)CaH3CbH3), 1.17 (d,
J¼7.0 Hz, 3H, C(6)CH3), 1.19–1.32 (m, 2H, C(9)HaHb,
C(10)HaHb), 1.34–1.41 (m, 1H, C(14)HaHb), 1.38 (s,
3H, C(4)CaH3CbH3), 1.44–1.58 (m, 2H, C(9)HaHb,
C(10)HaHb), 1.62–1.72 (m, 2H, C(8)H, C(11)HaHb), 2.00
(s, 3H, vinyl CH3), 2.08–2.14 (m, 1H, C(14)HaHb), 2.46
(dd, J¼2.2, 15.4 Hz, 1H, C(2)HaHb), 2.58 (dd, J¼10.7,
15.4 Hz, 1H, C(2)HaHb), 2.66 (br s, 1H, OH), 3.23–3.29 (m,
1H, C(6)H), 3.72–3.76 (m, 1H, C(7)H), 3.88 (br s, 1H, OH),
4.32 (br d, J¼10. 7 Hz, 1H, C(3)H), 4.71 (s, 2H, PyCH2O),
5.36–5.40 (m, 1H, C(15)H), 6.58 (s, 1H, vinyl H), 7.24
(d, J¼8.1 Hz, 1H, PyH), 7.69 (d, J¼8.1 Hz, 1H, PyH), 8.49
(s, 1H, PyH); 13C NMR (125 MHz, CDCl3) d 11.5, 13.7,
15.6, 15.7, 16.3, 18.4, 18.5, 22.1, 24.9, 30.7, 34.3, 35.6,
37.4, 39.1, 42.8, 53.6, 62.6, 71.4, 74.5, 79.5, 123.9, 124.7,
133.7, 135.2, 141.0, 147.8, 155.3, 170.8, 219.3; MALDI-
FTMS m/z 524.3004 (MNaþ), calcd for C29H43NO6Na
524.2982.
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