Synthesis of antifungal glucan synthase inhibitors from enfumafungin

Article abstract of DOI:10.1021/jo300046v

An efficient, new, and scalable semisynthesis of glucan synthase inhibitors 1 and 2 from the fermentation product enfumafungin 3 is described. The highlights of the synthesis include a high-yielding ether bond-forming reaction between a bulky sulfamidate 17 and alcohol 4 and a remarkably chemoselective, improved palladium(II)-mediated Corey-Yu allylic oxidation at the highly congested C-12 position of the enfumafungin core. Multi-hundred gram quantities of the target drug candidates 1 and 2 were prepared, in 12 linear steps with 25% isolated yield and 13 linear steps with 22% isolated yield, respectively.

Full text of DOI:10.1021/jo300046v

Article
pubs.acs.org/joc
Synthesis of Antifungal Glucan Synthase Inhibitors from
Enfumafungin
Yong-Li Zhong,* Donald R. Gauthier, Jr., Yao-Jun Shi, Mark McLaughlin, John Y. L. Chung,
Philippe Dagneau, Benjamin Marcune, Shane W. Krska, Richard G. Ball, Robert A. Reamer,
and Nobuyoshi Yasuda
Department of Process Research, Merck Research Laboratories, P.O. Box 2000, Rahway, New Jersey 07065-0900, United States
S
* Supporting Information
ABSTRACT: An efficient, new, and scalable semisynthesis of glucan synthase inhibitors 1 and 2 from the fermentation product
enfumafungin 3 is described. The highlights of the synthesis include a high-yielding ether bond-forming reaction between a bulky
sulfamidate 17 and alcohol 4 and a remarkably chemoselective, improved palladium(II)-mediated Corey-Yu allylic oxidation at
the highly congested C-12 position of the enfumafungin core. Multi-hundred gram quantities of the target drug candidates 1 and
2 were prepared, in 12 linear steps with 25% isolated yield and 13 linear steps with 22% isolated yield, respectively.
that the following three chemical modifications are required:
(1) reduction of the lactol group at position C-25; (2) removal
of the glucose and installation of the appropriate side chains at
C-3; and (3) allylic oxidation at C-12. Previous work5 at Merck
Research Laboratories and Scynexis Inc. indicated that the
allylic oxidation would only proceed reasonably well on a
substrate bearing an amide group at C-18. The overall synthetic
schemes for 1 and 2 looked amenable to scale-up, but we
identified a few potentially demanding steps. First of all, the use
of 2.5 equiv of KH (see 4 → 6, Scheme 1) was not advisible for
any large scale reaction. Second, while Birch-type or other
similar reductions (e.g., 6 → 7, Scheme 1) can be applied on
large scale, our preference was to avoid this transformation due
to the hazards represented by the handling of highly activated
elemental alkali metals and the requirement of special
apparatus.6 Third and most importantly, the allylic oxidation
required 45 equiv of CrO3 and 3,5-dimethylpyrazole in 380
volumes of CH2Cl2. The use of such a large excess of highly
toxic CrO3 and large volumes of a chlorinated solvent are not in
accordance green chemistry principles. In addition, we also had
difficulty removing residual chromium to acceptable levels in
the final products 1 and 2. Furthermore, the resulting enone
was found to be unstable in the crude reaction mixture,
requiring immediate silica gel column chromatography
purification to secure the oxidized product and leading to
unacceptably low yields upon scaling up to 10 g.
INTRODUCTION
■
The incidence of systemic fungal infections has risen
dramatically over recent decades due to the increasing number
of immunocompromised patients as well as the expanded use of
invasive medical procedures and broad spectrum antibiotics.1
The major antifungal therapeutic reagents for the treatment of
systemic fungal infections, including the polyenes, azoles, and
echinocandins, are often limited by their side effects, clinical
resistance, and a narrow spectrum of antifungal activity.2
Enfumafungin 33 isolated from a fermentation of Hormonema
sp. is capable of inhibiting fungal glucan synthase. As part of an
ongoing drug discovery program at Merck Research Labo-
ratories, two novel enfumafungin derivatives, 1 and 2, were
identified as potent glucan synthase inhibitors4 and selected for
further development.
Early syntheses5 of 1 and 2 involved 15 and 13 steps in the
longest linear sequence, respectively, with approximately 11%
and 17% yields. Besides the low overall yields, the original
procedures were not suitable for scale-up due to the use of
certain impractical and hazardous processes (vide infra). In
order to support further study of the pharmacological
properties of 1 and 2, efficient and reliable syntheses were
required. We report herein practical and scaleable syntheses of
1 and 2, including a detailed account of the issues presented by
these challenging substrates.
RESULTS AND DISCUSSION
■
Initial Medicinal Chemistry Route. The original medic-
inal chemistry route starting from 3 is summarized in Scheme 1.
In comparing our targets 1 and 2 with enfumafungin, it appears
Received: January 13, 2012
Published: March 16, 2012
© 2012 American Chemical Society
3297
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
Scheme 1. Medicinal Chemistry Route for 1 and 2
Scheme 2
In addition to the challenging synthetic problems presented
by targets 1 and 2, the issue of final crystalline form for the
active pharmaceutical ingredient (API) was not resolved at the
outset of our studies. Early isolations of 1 and 2 were via
lyophilization (amorphous solids), and so development of a
reproducible crystallization was also required.
Preparation of Benzyl Ester 4. The first three steps of the
synthesis of the benzyl ester 4 from enfumafungin 3 were
optimized as shown in Scheme 2. Hydroxyl acid 12 was
obtained from 3 by reduction of the lactol using Et3SiH and
TFA in toluene, followed by deglycosylation in methanol in the
presence of sulfuric acid. Crystalline 12 was isolated by direct
crystallization from MeOH/water (1:1) in 85% yield. It is
3298
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
worth noting that 12 needed to be washed with 5%
NaOAc(aq)/water (1:1) to ensure neutral pH prior to drying,
otherwise decomposition catalyzed by the remaining sulfuric
acid occurred.7 Facial selection of the methoxy group at C-2
position was perfectly controlled likely by neighboring
participation of the oxygen of the cyclic ether (11b). The
methyl ester of the carboxylic acid 12 is not formed under
refluxing MeOH/H2SO4 likely due to steric congestion that
inhibits nucleophilic attack at the carbonyl.8 In contrast,
selective benzylation of the carboxylic acid group in 12 was
accomplished with benzyl bromide and K2CO3 in DMF. The
reaction with K2CO3 was cleaner than the original reaction
conditions with NaHCO3, and isolated yield of crystalline
compound 12 was improved from 88% to 95% yield.
Installation of the Side Chain. Originally, installation of
the side chain of compounds 1 and 2 was achieved by SN2
opening of an N-tosylated aziridine with in situ preparation of
the potassium alkoxide of 4 using KH and 18-crown-6.5
However, subsequent removal of the N-tosyl protecting group
required the undesirable Birch reduction conditions alluded to
previously. Cyclic sulfamidates are known to be versatile
intermediates for the synthesis of various heteroatomic
functional compounds.9 We envisaged that the ether bond of
compounds 1 and 2 could be accessed through a ring opening
of a five-membered cyclic sulfamidate.
Table 1. Optimization for the Alkoxide-Mediated
Sulfamidate Opening
base
crown
b
T
t
conv
c
yield
d
a
entry
(equiv)
solvent
DME
ether
(°C) (h)
(%)
(%)
1
2
3
4
KH (2.0)
18-C-6
15-C-5
15-C-5
18-C-6
rt
rt
3
12
24
12
100
50
100
NaH (2.0) DME
NaH (2.0) DMAc
60
rt
70
e
KHMDS
(1.2)
DME
>90
<10
5
6
7
8
t-BuOK
THF/
DME
18-C-6
18-C-6
18-C-6
rt
rt
rt
rt
12
4
80
95
(1.2)
t-amylOK
(1.2)
DME
t-amylOK
(1.2)
DMAc
DMAc
2
>99
>99
>99
>99
t-amylOK
(1.2)
N/A
24
a
b
1.2 equiv of sulfamidate was used. 1 equiv of crown ether was used.
c
d
Measured by HPLC. The assay yields were measured by HPLC
e
against a quantitative standard. TMS silylation of alcohol 6 was the
major reaction.
(entry 4). Encouraging results were obtained when the reaction
was carried out with potassium tert-butoxide to give 80%
conversion (entry 5). Azeotropic removal of tBuOH from the
mixture of 4 and KOtBu to force the complete generation of
the potassium alkoxide of 4 failed even with extensive efforts.
The result indicated poor equilibrium toward the potassium
alkoxide in the reaction mixture. Fortunately, the coupling
reaction proceeded to almost quantitative yield when more
basic potassium tert-pentoxide (t-amylOK) was used instead of
KOtBu (entries 6−8). Also, the reaction worked well even
without 18-crown-6 (entry 8).
Since both 1 and 2 have a methyl group on the nitrogen
atom, N-methyl cyclic sulfamidate 17 was designed to
circumvent this problem. Sulfamidate 17 was prepared from
N-protected amino acid 1410 in three steps as shown in Scheme
3. Treatment of compound 14 with LAH afforded N-methyl
Scheme 3
Thus, after extensive optimization, amine 19 was obtained by
treatment of alcohol 4 and 1.2 equiv of sulfamidate 17 in the
presence of 1.2 equiv of potassium tert-pentoxide, followed by
HCl−NaOH aqueous workup. Crude amine 19 was then
heated with acetic acid in the presence of 2.49 equiv of p-
toluenesulfonic acid monohydrate and acetic anhydride,
followed by crystallization from acetonitrile/water (4:1) to
afford colorless crystalline acetate 20 in 90% overall isolated
yield from alcohol 4 (Scheme 4). Once again, the stereo-
chemistry of C-2 position was completely controlled by the
neighboring participation of the oxygen of the cyclic ether as
previously mentioned.
Allylic Oxidation. The remaining chemical steps from 20
to target 1 were allylic oxidation and deprotection of the benzyl
ester. In order to shorten the reaction sequence, allylic
oxidations were screened from earlier intermediates, such as
20, N-Cbz 21, and N-Cbz carboxylic acid 22 (shown in Figure
1). Unfortunately, almost all allylic oxidations did not proceed
well under many reported conditions.11
Among 20, 13, and 22, allylic oxidation of 21 was rather
promising, and results are summarized in Table 2. Substrate 21
was prepared in 95% yield by treatment of the free amine 20
with Cbz-chloride under Schotten-Bauman conditions. Initial
attempts to oxidize 21 using CrO3 in the presence of 3,5-
dimethyl pyrazole in dichloromethane at ambient temperature
resulted in 60% conversion. However, the HPLC assay of
desired enone 23 was less than 5% yield (entry 1). The assay
yields were improved a little up to 12% (entry 2) and 22%
(entry 12) by Doyle’s [Rh2(CAP)4 and TBHP]11g,h,p and
Corey-Yu’s [Pd/C or Pd(OH)2 /C and TBHP]11n,o allylic
oxidation conditions, respectively. However, these improve-
amino alcohol 15 in 93% yield, which was converted to
sulfamidite 16 by treatment with thionyl chloride in the
presence of Hunig’s base. Direct oxidation of crude sulfamidite
̈
16 with NaIO4 in the presence of catalytic amount of RuCl3
afforded desired crystalline sulfamidate 17 in 78% overall yield.
Upon crystallization of 17, a little upgrade of ee was observed.
With both alcohol 4 and sulfamidate 17 in hand, preliminary
investigation confirmed that the SN2 reaction coupling these
two fragments did proceed in the presence of KH and 18-
crown-6. Amine 19 was isolated in >90% yield via sulfamide 18
after adjustment of pH. However, the use of large amount of
pyrophoric KH is not recommended from a safety point of
view, so alternative bases were screened for the SN2
displacement reaction, including NaH, KHMDS, KOtBu, and
potassium tert-pentoxide in place of potassium hydride. As
shown in Table 1, using NaH as base in DME or DMAc in the
presence of 15-crown-5 ether afforded 50% and 70%
conversion, respectively (entries 2 and 3). The coupling
reaction using KHMDS as base gave high conversion but
provided O-TMS silylated compound 4 as the major product
3299
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
Scheme 4
tetrasubstituted unconjugated position, followed by further
oxidation, resulted in decomposition.
In a model study on the enfumafungin core skeleton without
the side chain,12 it was found that the allylic oxidation
proceeded rather smoothly when the carboxylic acid at C-18
was converted to the corresponding carbamide, and the desired
enone product was isolated in 40% yield under Doyle’s
conditions. Thus, it was decided allylic oxidation would be
performed on the N-Cbz-protected corresponding carbamide 8.
Removal of benzyl group from 20 via transfer hydrogenation
with a mixture of formic acid and triethylamine in the presence
of Pd/C gave amino acid 24 in 98% HPLC yield against to a
quantitative standard (Scheme 5). Without isolation of 24,
protection of the amine at the side chain was accomplished by
Cbz chloride. Because the carboxylic acid reacted with Cbz
chloride to form a stable mix-anhydride under Schotten-
Bauman conditions, 2.5 equiv of Cbz-chloride was required to
Figure 1. Substrates 21 and 22 for allylic oxidation.
ments of yield were not sufficient to run this oxidation on a
larger scale, especially since we had only a very limited supply
of expensive fermentation product starting material enfuma-
fungin.
Subsequent controlled experimental studies showed that
product 23 was unstable under the reaction conditions with or
without oxidants. The double bond migration of 23 to the
Table 2. Optimization for the Allylic Oxidation of Benzyl Ester 21
entry
catalyst
additive
oxidant
solvent
T (°C)
t (h)
conv (%)
23 (%)
a
1
3,5-DMP
K2CO3
K2CO3
K2CO3
pyridine
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Cs2CO3
K2CO3
CrO3
CH2Cl2
CH2Cl2
MeCN
rt
rt
48
42
60
70
40
41
10
50
44
61
64
50
92
58
<5
a
2
Rh2(CAP)4
Rh2(CAP)4
Pd/C
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
12
a
3
rt
42
<5
a
4
MeCN
30
rt
21
12
0
5
Pd(OTf)2
CH2Cl2
CH2Cl2
MeCN
48
b
a
a
a
a
a
b
6
Pd(OH)2/C
Pd(OH)2/C
Pd(OH)2/C
Pd(OH)2/C
Pd(OH)2/C
Pd(OH)2/C
Pd(OH)2/C
30
30
30
5
60
10
13
15
17
15
13
7
21
8
EtOAc
24
9
EtOAc
62
10
11
12
n-C3H7CN
n-C3H7CN
n-C3H7CN
5
62
−5
−30
384
288
a
TBHP
b
17 (22)
a
Assay yield by HPLC against a quantitative standard. Isolated yield.
3300
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
Scheme 5
Table 3. Optimization of the Allylic Oxidation of Amide 8
b
entry
catalyst
additive
oxidant
T (°C)
t (h)
conv (%)
9:27
9 (%)
a
1
2
3
3,5-DMP
K2CO3
CrO3
−25 to 15
21
70
31
100
>97
>97
36
30
34
Rh2(CAP)4
TBHP
TBHP
rt
1.3:1
1.3:1
Pd(OH)2/C
K2CO3
rt
a
b
3,5-Dimethylpyrazole. Assay yield by HPLC against a quantitative standard.
ensure the completion of N-Cbz protection. Selective
hydrolysis of the resulting mixture anhydride 25 required
unusually harsh conditions, heating with aqueous sodium
hydroxide, and provided N-Cbz carboxylic acid 22 in high assay
yield after removal of benzyl alcohol by a DMSO/water wash.
Isolated acid 22 was converted to the corresponding stable
ketene 26 by heating at 35 °C with EDC, and reaction of
ketene 26 with ammonia at 40 °C gave the desired amide in
89% yield.13
With amide 8 in hand, we initiated our detailed studies on its
allylic oxidation (Table 3). As mentioned previously, the initial
medicinal chemistry conditions for this step involved 45 equiv
of CrO3 and 45 equiv of 3,5-dimethylpyrazole in 380 vol of
CH2Cl2. By reducing the quantity of reagents and solvent
[CrO3 (15 equiv) and 3,5-dimethylpyrazole (15 equiv) in 50
vol of CH2Cl2], the isolated yield of the desired enone 9
decreased to 36% (Table 3, entry 1). Further decreasing the
excess of reagents and solvent (5 equiv and 15 vol] resulted in
low conversion and low assay yield of 9. Rh2(CAP)4-mediated
allylic oxidation of compound 8 by TBHP afforded a mixture of
enone 9 and allylic tert-butylperoxy ether 27 in 1.3:1 ratio
(entry 2) with an isolated yield of enone 9 of 30% after
chromatographic purification. A similar result was observed
with the allylic oxidation mediated by Pd(OH)2/C (entry 3).
The stereochemistry of peroxide 27 was confirmed by NOE
experiments as being β. As shown in Figure 2, when the
protons of the tert-butyl group of 27 were irradiated, besides
the olefin proton and C-12 proton, NOE enhancements to the
proton of C-18 (0.5%), the C-26 methyl (0.5%), and the α-
proton of C-25 (0.9%) were observed.
It is well documented that allylic tert-butylperoxy ethers such
as 27 are readily converted to the corresponding enone under
typical reaction conditions.14 In practice, we did not observe
any corresponding α-peroxide ether, which was apparently
3301
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
hydroperoxide (CHP) instead of tert-butylhydroperoxide, was
employed. Indeed, with CHP as oxidant the ratio of desired
product 9 to peroxides (27 + 30) improved to ∼7:1 while
HPLC assay yield increased to 64% from 34%.15
Completion of the Synthesis. With enone 9 in hand, the
primary amide was converted to the acid 10 by treatment with
tert-butyl nitrite in aqueous acetonitrile in 83% isolated yield
after crystallization. Finally, cleavage of the N-Cbz-protected
group by hydrogenation in the presence of Pd(OH)2/C and
acetic acid afforded drug candidate 1 in 98% yield after
crystallization from ethyl acetate and methanol. Reductive N-
methylation of 1 with formaldehyde in the presence of sodium
cyanoborohydride furnished the synthesis of the second drug
candidate 2 in 90% yield after crystallization from isopropanol,
as summarized in Scheme 6.
Treatment of compound 1 with sodium bicarbonate,
following by hydrogen chloride in isopropanol afforded
crystalline compound 31 in 86% overall yield. Single crystals
of compound 31 as an acetonitrile solvate were grown from
acetonitrile, and an X-ray structure was obtained (Figure 4).
The absolute configuration of 33 was assigned as R at C2, C3,
C5, C8, C10, C14, C17, C18, and C21; the conformations at
C4, C13, and C34 were assigned as S.16
In conclusion, we have developed a practical, scaleable, and
novel synthesis of glucan synthase inhibitors 1 and 2. Notable
features include a high-yielding ether bond formation between
sulfamidate 17 and alcohol 4, a highly efficient 5-step “through
process” without isolation of intermediates for the synthesis of
amide 8 from benzyl ester 20, and a remarkable chemoselective,
improved palladium(II)-mediated allylic oxidation by cumene
hydroperoxide. Multi-hundred gram quantities of the target
drug candidates 1 and 2 were synthesized in 12 linear steps
with 25% isolated yield and 13 linear steps with 22% isolated
yield, respectively.
Figure 2. NOE Studies for 27.
instantly converted to enone 9. In contrast, the β-peroxide
ether 27 was remarkably stable under the reaction conditions.
Conversion of 27 to 9 was attempted under numerous
conditions including treatment of 20 with base (e.g., TEA,
DBU, K2CO3), transition metals (e.g., CuCl, CuCl2, NiCl2,
CoCl2, FeCl3, Pd/C with or without TBHP), and UV lamp at
low or high temperature. All conditions resulted in no reaction
or decomposition.
The surprising inertness of this β-peroxide directed our
attention to the stereochemical aspects of this system. As
reported by Corey and Yu,11n,o the allylic oxidation proceeds by
a radical mechanism and allylic radical 28 would be the
expected intermediate for this reaction (Figure 3). Considering
the stereochemical environment of radical 28, it was not
surprising that a nucleophilic (tBuO2M) would more readily
approach the molecule from the α-face than from the β-face
due to a 1,3-diaxial interaction with the C-26 methyl groups.
Peroxide attack from the α-face produced an unobserved
hypothetical peroxide intermediate 29, which spontaneously
collapses to enone 9 with abstraction of a C-12 axial proton
either by base or by the tert-butylperoxy radical. On the other
hand, a nucleophilic attack from the β-face generates the stable
tert-butylperoxy ether 27, in which the C-12 equatorial proton
cannot readily be abstracted, either by a base or by a tert-
butylperoxy radical under the allylic oxidation conditions. The
reason why this abstraction is so kinetically disfavored is not
clear. It might be worth noting that the C ring of 27 would be
expected to adopt a twisted boat conformation in which the C-
12 equatorial proton would be forced to move into a sterically
congested pocket.
EXPERIMENTAL SECTION
■
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-2-Hydroxy-3-me-
thoxy-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradeca-hydro-1H-
1,4a-(methanooxymethano)chrysene-7-carboxylic Acid (12).5
To a 100 L four-neck round-bottom flask equipped with an overhead
stirrer, a thermocouple, and a nitrogen inlet were charged
enfumafungin 3 (4.000 kg, 5.643 mol) and dichloromethane (22.4
L). To the resulting slurry was charged triethylsilane (2.620 kg, 22.53
mol) in one portion. To the resulting mixture was slowly added TFA
Since the β-face of the radical intermediate 28 is more
hindered than the α-face, the ratio of enone 9 and peroxide 27
would be improved if a bulkier oxidant, such as cumene
Figure 3. Proposed mechanism for the selectivity of allylic oxidation.
3302
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
Scheme 6
Figure 4. X-ray structure of compound 31. The thermal ellipsoids represent 50% probability contours, while the H atoms are drawn at an arbitrary
size. For clarity the water and acetonitrile solvent molecules along with the Cl counterion have been omitted.
(7.250 kg, 63.59 mol) over 35 min while maintaining the temperature
<30 °C. The reaction mixture was stirred at rt for 0.5 h (>99%
conversion).
MeOH/3% NaOAc aqueous (1:1, 20 L), cold MeOH/water (1:1, 20
L), and heptanes (10 L) and dried under vacuum with nitrogen to
afford acid 12 (2.548 kg, 90% isolated yield), mp 266.7−267.3 °C.
1
The dichloromethane was concentrated to a low volume. To the
solution was added methanol (2 × 11.2 L) and concentrated down to
a low volume. To the resulting slurry was charged methanol (40 L)
and then slowly 96% sulfuric acid (1.680 L, 30.26 mol) was added. The
reaction flask was equipped with a condenser. The reaction mixture
was refluxed for 14 h to form white slurry and then cooled to 6 °C. To
the slurry was added cold water (40 L) over 10 min. The reaction
mixture was stirred at 10 °C for 0.5−1 h. The crystalline solid was
collected by filtration, washed by cold MeOH/water (1:1, 20 L), cold
[α]20 −73.0° (THF, c = 1.0). H NMR (500 MHz, CDCl3) δ: 5.46
D
(m, 1 H), 4.16 (m, 1 H), 3.77 (d, J = 11.5 Hz,1 H), 3.43 (s, 3 H), 3.31
(d, J = 11.5 Hz, 1 H), 3.18 (d, J = 8.5 Hz, 1 H), 2.86 (s, 1 H), 2.44 (dd,
J = 13.3, 6.8 Hz, 1 H), 2.15 (m, 1 H), 2.03 (m, 1 H), 1.95 (m, 1 H),
1.82−1.70 (m, 3 H), 1.65−1.36 (m, 5 H), 1.25 (s, 3 H), 1.28−1.22
(overlapped, m, 4 H), 1.20 (s, 3 H), 1.14 (s, 3 H), 0.89 (d, J = 6.7 Hz,
3 H), 0.84 (d, J = 6.7 Hz, 3 H), 0.80 (s, 3 H), 0.76 (d, J = 7.1 Hz, 3 H),
0.72 (s, 3 H). 13C NMR (125 MHz, DMSO-d6) δ: 176.3, 143.4, 120.6,
82.0, 81.1, 72.7, 66.0, 58.2, 53.0, 48.5, 45.9, 41.2, 40.7, 40.3, 40.0, 39.2,
3303
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
38.4, 38.3, 38.2, 29.6, 28.7, 27.2, 25.9, 21.4, 19.8, 19.4 (2 C), 18.9, 17.2,
16.7, 9.1. HRMS (ESI) calculated for C31H50O5: 503.3731 (M + H)+,
found 503.3725. Anal. Calcd for C31H50O5: C, 74.06; H, 10.02. Found:
C, 73.78; H, 9.86.
mixture was stirred at −3 °C for 1 h (the reaction was monitored by
1H NMR).
Water (8 L) was slowly added to the reaction mixture. After phase
separation, the organic layer was washed by water (8 L × 1). The
resulting crude sulfamidite intimidate was purified by passing through
silica gel (8.30 kg) plug eluting with heptane/EtOAc (3:1) to give
relative pure sulfamidite intermediate (1.980 kg).
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-Benzyl-2-hy-
droxy-3-methoxy-1,6a,8,10a-tetramethyl-8-((R)-3-methylbu-
tan-2-yl)-2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahy-
dro-1H-1,4a-(methanooxymethano)chrysene-7-carboxylate
(4).5 To a 75 L four-neck round-bottom flask equipped with an
overhead stirrer, a thermocouple, and a nitrogen inlet were charged the
acid 12 (2.600 kg, 5.172 mol), potassium carbonate powder (0.786 kg,
5.687 mol), and DMF (13 L, KF = 78 ppm). To the resulting slurry
was then added benzyl bromide (0.973 kg, 5.690 mol) at 25−35 °C.
The reaction mixture was then warmed to 78 °C over 0.5 h, and a
complete conversion (>99%) was obtained.
The mixture was cooled to 17 °C by ice−water bath, and ethanol
(6.0 L) was added. Then, water (9.0 L, 3.5 vol) was slowly added to
the reaction mixture at 17 to 21 °C over 1 h. The resulting slurry was
stirred at that temperature for 1 h. The crystalline solid was collected
by filtration, washed with water/EtOH (1:1, 10 L), and dried under
vacuum with nitrogen sweep for 48 h to afford 2.902 kg of the desired
To a 75 L four-neck round-bottom, equipped with an overhead
stirrer, a thermocouple, and a nitrogen inlet were charged NaIO4
(2.790 kg, 13.04 mol), acetonitrile (7.4 L), catalytic amount of
RuCl3·xH2O (0.0185 kg, 0.090 mol), and the mixture was cooled to 7
°C. Sulfamidite (1.980 kg) in acetonitrile (3 L) was slowly added to
the reaction mixture over 1.6 h. The reaction was stirred at rt for about
1
1 h. (The reaction was monitored by H NMR.)
The resulting slurry was diluted with IPAc (12 L) and water (4 L).
Some insoluble solids were filtered off and washed by IPAc (12 L × 1).
The combined filtrates were phase separated. The organic layer was
washed by water (4 L × 1) and 15% brine (4 L × 1) and concentrated
to give crude product sulfamidate 17 as a solid.
The crude sulfamidate 17 was dissolved in IPAc (2 L). Heptane (2
L) was slowly added and seeded to crystallize. To the resulting slurry
was slowly added heptane (4 L) over 1 h, and the mixture was stirred
at rt for 0.5 h. Then the slurry was stirred at 2−4 °C for 1.5 h. The
crystalline solid was collected, washed with cold heptane/EtOAc (5:1,
2 L) and heptane (2 L), and dried under vacuum with nitrogen sweep
benzyl ester 4 (95% isolated yield) as white solid, mp 192.4−193.5 °C.
1
[α]20 −36.5° (CHCl3, c = 1.0). H NMR (400 MHz, CDCl3) δ:
D
7.38−7.29 (m, 5 H), 5.41 (m, 1 H), 5.11 (d, J = 12.3 Hz, 1 H), 4.98
(d, J = 12.3 Hz, 1 H), 4.14 (m, 1 H), 3.77 (d, J = 11.8 Hz, 1 H), 3.43
(s, 3 H), 3.41−3.37 (m, 2 H), 3.30 (d, J = 11.8 Hz, 1 H), 3.17 (d, J =
8.6 Hz, 1 H), 2.87 (s, 1 H), 2.50−2.40 (m, 2 H), 2.11 (m, 1 H), 2.02
(br d, J = 13.0 Hz, 1 H), 1.92 (br d, J = 17.8 Hz, 1 H), 1.82−1.69 (m, 3
H), 1.60−1.34 (m, 5 H), 1.30−1.24 (m, 3 H), 1.23 (s, 3 H), 1.15 (m, 1
H), 1.14 (s, 3 H), 0.81 (d, J = 6.8 Hz, 3 H), 0.80 (s, 3 H), 0.77 (d, J =
6.8 Hz, 3 H), 0.72 (d, J = 7.1 Hz, 3 H), 0.71 (s, 3 H). 13C NMR (100
MHz, CDCl3) δ: 173.8, 141.8, 136.0, 128.5 (2 C), 128.4 (2 C), 128.0,
120.0, 80.9, 80.7, 72.1, 65.5, 65.1, 56.8, 52.6, 47.9, 43.8, 40.7, 40.0,
39.5, 38.3 (2 C), 38.2, 37.4, 37.2, 28.9, 27.8, 26.3, 24.6, 20.3, 18.7, 18.4,
18.3, 17.6, 16.3, 15.6, 8.0. HRMS (ESI) calculated for C38H56O5:
610.4471 (M + NH4)+, found 610.4481. Anal. Calcd for C38H56O5: C,
76.99; H, 9.52. Found: C, 76.69; H, 9.66.
to afford sulfamidate 17 (1.850 kg, 78% overall yield, > 97% ee), mp
1
58.9−59.6 °C. [α]20 −9.1° (MeOH, c = 0.91). H NMR (500 MHz,
D
CDCl3) δ: 4.38 (d, J = 8.8 Hz, 1 H), 4.06 (d, J = 8.8 Hz, 1 H), 2.65 (s,
3 H), 1.85 (m, 1 H), 1.32 (s, 3 H), 0.94 (d, J = 6.9 Hz, 3 H), 0.89 (d, J
= 6.9 Hz, 3 H). 13C NMR (125 MHz, CDCl3) δ: 73.1, 65.5, 34.0, 26.5,
19.6, 16.8, 16.6. HRMS (ESI) calculated for C7H15NO3S: 194.0845
(M + H)+, found 194.0837. Anal. Calcd for C7H15NO3S: C, 43.50; H,
7.82; N, 7.25. Found: C, 43.23; H, 7.95; N, 7.18.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-Benzyl 2-((S)-2,3-
dimethyl-2- (methylamino)butoxy)-3-methoxy-1,6a,8,10a-tet-
r a m e t h y l - 8 - ( ( R ) - 3 - m e t h y l b u t a n - 2 - y l ) -
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-1,4a-
(methanooxymethano)chrysene-7-carboxylate (19). To a 75 L
four-neck round-bottom flask equipped with an overhead stirrer, a
thermocouple, and a nitrogen inlet were charged with sulfamidate 17
(1.063 kg, 5.500 mol) and ester 4 (2.711 kg, 4.573 mol) in toluene (29
L) were azotropically dried to provide a small volume of the toluene
solution (<10 L, KF < 200 ppm). The required DMAc (20 L, KF = 78
ppm) was added to provide a solution (KF = 188 ppm) at room
temperature.
To the above solution was slowly added potassium tert-pentoxide
(PTP) solution (3.23 L, 5.500 mol) via an additional funnel at 20−25
°C over 0.5 h. The reaction mixture was stirred at rt for 24 h (100%
conversion). IPAc (10 L) was added to the reaction mixture, followed
by addition of 5 N HCl (3.3 L) and water (5.7 L). The resulting
mixture was stirred for 0.5 h. Five normal NaOH (4 L) was added
slowly to bring the pH to 11.2 as indicated by a pH meter. The
mixture was transferred to a 100 L vessel. The 75 L round-bottom was
rinsed with additional IPAc (14 L) and water (18 L) and then
transferred to the 100 L vessel. After being stirred for ∼0.5 h, the
aqueous layer was separated and then extracted with IPAc (25 L × 1).
The combined IPAc layers were washed with 5% K2CO3 (18 L × 1)
and then water (18 L × 2). The organic layer was collected and
assayed by HPLC against to pure standard to give desired amine 19
(3.132 kg, 97% HPLC yield).
(S)-2,3-Dimethyl-2-(methylamino)butan-1-ol (15).17 To a 100
L four-neck round-bottom, equipped with an overhead stirrer, a
thermocouple, and nitrogen inlet was charged 2 M LiAlH4 in THF
solution (16.4 L, 32.50 mol). The carbamate acid 14 (5.040 kg, 13.11
mol) in α-Me-THF and THF solution (8 L, total vol) was slowly
added over 2 h and 25 min. The reduced reaction was exothermic. The
reaction mixture was heated at 60 °C for 8 h.
Then, the reaction mixture was cooled to 5 °C. Water (1.5 L) was
added dropwise over 3 h and 20 min at a temperature 18−24 °C. The
addition was exothermic with vigorous gas generation! The reaction
mixture turned to a thick white slurry. One normal NaOH aqueous (5
L, 25.00 mol) was added over 50 min at 20−24 °C, and the mixture
was stirred for 10 min. The solid was filtered off and washed by THF
(5 L × 5), with displacement wash by THF (5 L × 3), slurry wash by
THF (10 L × 1), and displacement wash by THF (10 L × 1).
The combined filtrates were concentrated and flushed with α-Me-
THF until the KF of the solution ≤400 ppm at a total volume 5.5 L.
The solution was concentrated to an oil and cooled to crystallize. The
resulting off white waxy solid was dried on a rotavapor and then high
vacuum for 1.5 h to afford aminoalcohol 15 (1.610 kg, 94% yield) as a
1
wax. [α]20D −7.5° (MeOH, c = 1.3). H NMR (400 MHz, CDCl3) δ:
3.37 (s, 2 H), 2.49 (broad s, 2 H), 2.27 (s, 3 H), 1.85 (m, 1 H), 0.91
(s, 3 H), 0.89 (d, J = 7 Hz, 3 H), 0.85 (d, J = 7 Hz, 3 H). 13C NMR
(100 MHz, CDCl3) δ: 64.0, 58.5, 30.5, 27.5, 17.2, 16.9, 16.6. HRMS
(ESI) calculated for C7H17NO: 132.1383 (M + H)+, found 132.1380.
(S)-4-Isopropyl-3,4-dimethyl-1,2,3-oxathiazolidine 2,2-diox-
ide (17). To a 75 L four-neck round-bottom, equipped with an
overhead stirrer, a thermocouple, and a nitrogen inlet were charged
aminoalcohol (1.610 kg, 12.27 mol), dichloromethane (14.5 L), and
DIEA (4.700 L, 26.99 mol). The resulting solution was cooled to −17
°C. Thionyl chloride (0.982 L, 13.50 mol) in dichloromehane (1.60 L)
was added dropwise over 1.6 h at a temperature −8 to −4 °C. The
reaction went from colorless to a deep red solution. The reaction
A small amount of the solution was concentrated and crystallized in
IPAc to give crystalline 19, mp 235.7−236.4 °C. [α]20 −34.5°
D
1
(CHCl3, c = 1.0). H NMR (400 MHz, CDCl3) δ: 7.39−7.30 (m, 5
H), 5.41 (m, 1 H), 5.11 (d, J = 12.3 Hz, 1 H), 4.98 (d, J = 12.3 Hz, 1
H), 4.15 (m, 1 H), 3.84 (d, J = 9.3 Hz, 1 H), 3.71 (d, J = 11.6 Hz, 1
H), 3.42−3.34 (m, 5 H), 3.27 (d, J = 11.6 Hz, 1 H), 2.87 (s, 1 H), 2.82
(d, J = 8.4 Hz, 1 H), 2.4 (dd, J = 13.4, 6.9 Hz, 1 H), 2.33 (s, 3 H), 2.11
(m, 1 H), 2.06 (m, 1 H), 1.93−1.80 (m, 2 H), 1.77−1.68 (m, 3 H),
1.59−1.34 (m, 5 H), 1.26−1.24 (m, 2 H), 1.23 (s, 3 H), 1.20−1.16
(m, 2 H), 1.15 (s, 3 H), 0.95 (d, J = 6.8 Hz, 3 H), 0.95 (s, 3 H), 0.90
3304
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
(d, J = 6.8 Hz, 3 H), 0.81 (d, J = 6.7 Hz, 3 H), 0.78 (d, J = 7.0 Hz, 3
H), 0.77 (s, 3 H), 0.72 (d, J = 6.5 Hz, 3 H), 0.71 (s, 3 H). 13C NMR
(100 MHz, CDCl3) δ: 173.9, 142.1, 136.2, 128.7 (2 C, 128.5 (2 C),
128.2, 120.2, 88.4, 81.9, 74.8, 72.4, 66.2, 65.7, 56.4, 52.8, 48.1, 44.7,
40.8, 39.8, 39.7, 39.6, 38.4, 38.3, 37.5, 37.4, 31.5, 29.1, 28.1, 28.0, 26.5,
24.8, 21.9, 20.5, 19.1, 18.6, 18.4, 18.1, 17.6, 17.4, 17.0, 16.5, 15.8, 8.1.
HRMS (ESI) calculated for C45H71NO5: 706.5405 (M + H)+, found
706.5415. Anal. Calcd for C45H71NO5: C, 76.55; H, 10.14; N, 1.98.
Found: C, 76.32; H, 10.25; N, 1.90.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-Benzyl 3-acetoxy-
2-((S)-2,3-dimethyl-2-(methylamino)butoxy)-1,6a,8,10a-tetra-
m e t h y l - 8 - ( ( R ) - 3 - m e t h y l b u t a n - 2 - y l ) -
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-1,4a-
(methanooxymethano)chrysene-7-carboxylate (20). To a 50 L
four-neck round-bottom flask equipped with an overhead stirrer, a
thermocouple, and a nitrogen inlet was charged the IPAc solution of
the amine 19 (3.132 kg, 4.436 mol) obtained from the previous step.
The mixture was concentrated. When it was concentrated to a small
volume (<8 L) at 20−25 °C, a light slurry was observed. After being
stirred at rt for 2 days, slurry of crystalline amine 19 was obtained.
AcOH (8 L) was slowly fed in under the vacuum-distillation for the
solvent switch. An acetic acid solution of amine 19 was obtained after
additional AcOH was added (4 L and then 3.2 L) and assayed by
HPLC against standard to be ∼20 wt % of the amine 19 (or ∼4 vol of
AcOH, KF at 732 ppm). To the resulting solution was added solid
TsOHc·H2O (2.101 kg, 11.05 mol), followed by addition of Ac2O
(2.256 kg, 22.10 mol) at rt over 0.5 h to afford a clear solution (an
increase of temperature from 19 to 30 °C was observed).
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-Benzyl-3-acetoxy-
2-((S)-2-(((benzyloxy)carbonyl)(methyl)amino)-2,3-dimethyl-
butoxy)-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-1,4a-
(methanooxymethano)chrysene-7-carboxylate (21). To a 1 L
three-neck round-bottom flask equipped with an overhead stirrer, a
thermocouple, and a nitrogen inlet were charged the acid 20 (50.00 g,
0.06811 mol), potassium carbonate powder (10.36 g, 0.07493 mol),
and DMF (171 mL, KF = 78 ppm). To the resulting slurry was then
added benzyl bromide (12.81 g, 0.07493 mol) at 25−35 °C. The
reaction mixture was then warmed to 78 °C over 0.5 h, and a complete
conversion (>99%) was obtained.
The mixture was cooled to 17 °C by ice−water bath, and ethanol
(115 mL) was added. Then, water (175 mL, 3.5 vol) was slowly added
to the reaction mixture at 17 to 21 °C over 1 h. The resulting slurry
was stirred at that temperature for 1 h. The crystalline solid was
collected by filtration, washed with water/EtOH (1:1, 192 mL), and
dried under vacuum with nitrogen sweep for 48 h to afford desired
benzyl ester 21 (57.94 g, 98% isolated yield) as white solid, mp 103.1−
1
103.9 °C. [α]25 −50.8° (MeOH, c = 0.25). H NMR (400 MHz,
D
CDCl3) δ: 7.38−7.27 (m, 10 H), 5.67 (m, 1 H), 5.37 (m, 1 H), 5.11
(m, 2 H), 4.98 (d, J = 12.5 Hz, 1 H), 4.94 (d, J = 12.5 Hz, 1 H), 4.40
(m, 1 H), 3.72 (d, J = 11.7 Hz, 1 H), 3.47 (d, J = 11.9 Hz, 1 H), 3.43
(d, J = 8.8 Hz, 1 H), 3.34 (dd, J = 11.9, 2.0 Hz, 1 H), 3.28 (d, J = 11.7
Hz, 1 H), 2.99 (d, J = 9.2 Hz, 1 H), 2.96 (s, 3 H), 2.85 (s, 1 H), 2.81
(m, 1 H), 2.44 (dd, J = 13.2, 7.0 Hz, 1 H), 2.10 (m, 1 H), 2.07 (s, 3
H), 1.98 (m, 1 H), 1.86 (m, 1 H), 1.77−1.66 (m, 3 H), 1.53 (s, 3 H),
1.50−1.32 (m, 3 H), 1.29 (s, 3 H), 1.25−1.19 (overlapped, m, 2 H),
1.21 (s, 3 H), 1.17 (m, 1 H), 1.12 (s, 3 H), 0.81 (d, J = 7.0 Hz, 6 H),
0.80 (d, J = 6.7 Hz, 3 H), 0.77 (d, J = 7.0 Hz, 3 H), 0.75 (s, 3 H), 0.71
(d, J = 7.1 Hz, 3 H), 0.69 (s, 3 H). 13C NMR (100 MHz, CDCl3) δ:
173.8, 170.6, 155.7, 141.2, 137.3, 136.0, 128.6 (2 C), 128.5 (2 C),
128.3 (2 C), 128.2, 127.8 (2 C), 127.6, 120.5, 86.0, 76.6, 75.8, 72.2,
66.3, 65.8, 65.6, 64.5, 52.5, 47.9, 44.5, 40.7, 40.2, 39.9, 39.6, 38.5, 38.2,
37.4, 37.2, 33.4, 30.7, 28.9, 27.8, 26.4, 24.7, 21.7, 20.4, 19.0, 18.4, 18.3,
17.8, 17.7, 17.2 (2 C), 16.4, 15.6, 8.0. HRMS (ESI) calculated for
C54H77NO8: 868.5722 (M + H)+, found 868.5728. Anal. Calcd for
C54H77NO8: C, 74.70; H, 8.94; N: 1.67. Found: C, 74.88; H, 9.21; N:
1.58.
The solution was then heated to about 60 °C for 3 h. It was allowed
to cool to rt and stirred overnight. A portion of AcOH (∼1/2 of
AcOH added) was removed by distillation under vacuum at 18−30 °C,
and the remaining mixture was diluted with IPAc (30 L) and then
transferred to 100 L vessel. Additional IPAc (10 L) was used to rinse
the 100-L RBF and then transferred.
The above solution was cooled to 20 °C, and 5 N NaOH was slowly
added while maintaining the temperature at <25 °C until the pH 11.5
as indicated on a pH meter. The aqueous layer was separated, and the
organic layer washed with 5 wt % K2CO3 (18 L × 1) and then water
(16 L × 1). The IPAc layer was collected and assayed by HPLC
against standard to give 3.150 kg of compound 20 (97% HPLC yield).
The resulting solution was concentrated and solvent-switched to
MeCN to provide slurry of the product. It was concentrated down to
∼22 L of batch size (7 vol of MeCN). The resulting slurry was stirred
at 20 °C for 0.5 h, and then water (5 L) was added over 1 h. The batch
temperature was cooled to 10−14 °C. The slurry was stirred at 10−14
°C for 2 h. The second portion of water (4 L) was added at 10 °C over
0.5 h. The slurry was warmed to 17 °C and stirred for 1 h. The
crystalline product 20 was collected by filtration, rinsed with the mixed
solvents (1/2 MeCN/H2O, 4 L × 2), and then dried in the filter pot
under vacuum and with nitrogen sweep to provide 3.011 kg of a white
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-Benzyl-3-acetoxy-
2-((S)-2-(((benzyloxy)carbonyl)(methyl)amino)-2,3-dimethyl-
butoxy)-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-6-
oxo-2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-
1,4a-(methanooxymethano)chrysene-7-carboxylate (23). To a
100 mL three-neck round-bottom flask equipped with an overhead
stirrer, thermocouple, dropping funnel, and nitrogen inlet were
charged alkene 21 (4.250 g, 4.891 mmol), propionitrile (50 mL),
and potassium carbonate (0.169 g, 1.223 mmol), and the mixture was
cooled to −30 °C. To the resulting solution were added 37 wt %
Pd(OH)2/C (0.2798 g, 15 mol %) and potassium carbonate powder
(0.169 g, 25 mol %), respectively. Five molar tert-butyl hydroperoxide
in acetonitrile (TBHP, 9.80 mL, 48.91 mmol) was added, and the
mixture was stirred at −30 °C for 96 h. Then, 10 mol % of 37 wt %
Pd(OH)2/C (0.1666 g) and another portion of 5.0 M of TBHP (4.90
mL, 24.46 mmol) were added, respectively. The mixture was stirred at
−30 °C for another 96 h. The third 5 equiv of 5.0 M of TBHP (4.90
mL, 24.46 mmol) was added, and the mixture was stirred at the same
temperature for 96 h (58% conversion).
The catalyst was filtered off and washed by methylene chloride
(22% HPLC yield against to standard). The filtrate was solvent-
switched to MeOH (50 mL, total vol) at <10 °C. The resulting
methanol solution was slowly added to a 25 wt % Na2S2O3 (60 mL)
aqueous solution until the excess oxidant has been quenched. The
reaction mixture was extracted by toluene (30 mL × 2). The combined
organic layer was washed with 16% brine (15 mL). The organic layer
was concentrated and solvent-switched to heptane (10 mL, total vol).
The crude product was purified by Biotage (eluting with heptanes/
MTBE = 100:0 to 5:1) to give desired product N-Cbz enone amide 23
solid 20 (90% overall isolated yield from compound 4), mp 209.8−
1
211.0 °C. [α]20 −25.3° (MeOH, c = 1.0). H NMR (400 MHz,
D
CDCl3) δ: 7.37−7.28 (m, 5 H), 5.71 (m, 1 H), 5.37 (m, 1 H), 5.11 (d,
J = 12.2 Hz, 1 H), 4.93 (d, J = 12.2 Hz, 1 H), 3.72 (d, J = 11.7 Hz, 1
H), 3.62 (d, J = 8.8 Hz, 1 H), 3.46 (d, J = 11.6 Hz, 1 H), 3.35 (d, J =
11.6 Hz, 1 H), 3.33 (d, J = 8.7 Hz, 1 H), 3.28 (d, J = 11.7 Hz, 1 H),
3.02 (d, J = 8.8 Hz, 1 H), 2.85 (s, 1H), 2.46 (dd, J = 13.3, 7.1 Hz, 1 H),
2.22 (s, 3 H), 2.10 (m, 1 H), 2.01 (s, 3 H), 1.97 (m, 1 H), 1.88−1.67
(m, 6 H), 1.58−1.33 (m, 5 H), 1.26−1.20 (m, 6 H), 1.14 (m, 1 H),
1.12 (s, 3 H), 0.88 (d, J = 6.7 Hz, 3 H), 0.87 (s, 3 H), 0.83 (d, J = 6.9
Hz, 3 H), 0.80 (d, J = 6.8 Hz, 3 H), 0.78 (s, 3 H), 0.77 (d, J = 6.9 Hz, 3
H), 0.70 (d, J = 7.2 Hz, 3 H), 0.69 (s, 3 H). 13C NMR (100 MHz,
CDCl3) δ: 173.9, 170.4, 141.3, 136.1, 128.7 (2 C), 128.5 (2 C), 128.2,
120.6, 86.5, 76.2, 75.3, 72.3, 66.0, 65.7, 57.7, 52.7, 48.1, 44.6, 40.8,
40.3, 40.0, 39.6, 38.7, 38.3, 37.5, 37.3, 31.8, 29.1, 28.3 (2 C), 28.0, 26.5,
24.8, 21.7, 20.5, 19.1, 18.5, 18.4, 18.0, 17.5, 17.0, 16.5, 15.7, 8.1. HRMS
(ESI) calculated for C46H71NO6: 734.5354 (M + H)+, found 734.5364.
Anal. Calcd for C46H71NO6: C, 75.27; H, 9.75; N: 1.91. Found: C,
75.05; H, 9.82; N: 1.82.
(0.735 g, 17% isolated yield) as white solid, mp 110.2−111.1 °C.
1
[α]25 −25.9° (MeOH, c = 0.29). H NMR (500 MHz, CDCl3) δ:
D
7.48 (m, 2 H), 7.38−7.32 (m, 6 H), 7.31−7.27 (m, 2 H), 5.77 (d, J =
3305
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
2.4 Hz, 1 H), 5.70 (m, 1 H), 5.25 (d, J = 12.2 Hz, 1 H), 5.11 (d, J =
12.4 Hz, 1 H), 4.99 (d, J = 12.4 Hz, 1 H), 4.98 (d, J = 12.2 Hz, 1 H),
4.42 (m, 1 H), 3.76 (d, J = 11.7 Hz, 1 H), 3.53 (d, J = 11.4 Hz, 1 H),
3.44 (d, J = 8.6 Hz, 1 H), 3.40 (dd, J = 11.7, 2.2 Hz, 1 H), 3.28 (d, J =
11.4 Hz, 1 H), 3.12 (s, 1 H), 3.01 (d, J = 8.6 Hz, 1 H), 2.96 (s, 3 H),
2.81 (m, 1 H), 2.53−2.47 (m, 1 H), 2.15 (m, 1 H), 2.07 (s, 3 H),
1.87−1.80 (m, 4 H), 1.71 (s, 3 H), 1.70−1.61 (m, 2 H), 1.56 (m, 1 H),
1.46 (m, 1 H), 1.36−1.24 (overlapped, m, 4 H), 1.29 (s, 3 H), 1.09 (s,
3 H), 0.82 (d, J = 7.2 Hz, 6 H), 0.793 (s, 3 H), 0.791 (d, J = 6.8 Hz, 3
H), 0.78 (s, 3 H), 0.72 (d, J = 6.7 Hz, 3 H), 0.69 (d, J = 7.2 Hz, 3 H).
13C NMR (125 MHz, CDCl3) δ: 202.9, 174.2, 170.3, 161.9, 155.7,
137.4, 136.4, 128.8 (2 C), 128.3 (2 C), 128.2 (2 C), 127.8, 127.7 (2
C), 127.6, 123.1, 85.7, 77.6, 75.0, 70.8, 66.4, 66.0, 65.9, 64.5, 52.4, 46.0,
45.2, 43.2, 41.8, 41.1, 41.0, 40.9, 39.9, 38.2, 33.4, 30.7, 27.3, 26.7, 26.5,
24.2, 21.6, 21.5, 18.7, 18.6, 18.2, 17.8, 17.7, 17.2 (2 C), 15.6, 15.4, 8.0.
HRMS (ESI) calculated for C54H75NO9: 882.5515 (M + H)+, found
882.5520. Anal. Calcd for C54H75NO9: C, 73.52; H, 8.57; N: 1.59.
Found: C, 73.66; H, 8.56; N: 1.48.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-3-Acetoxy-2-((S)-
2,3-dimethyl-2-(methylamino)butoxy)-1,6a,8,10a-tetramethyl-
8-((R)-3-methylbutan-2-yl)-2,3,4,6,6a,7,8,9,10,10a,10b,-
11,12,12a-tetradecahydro-1H-1,4a-(methanooxymethano)-
chrysene-7-carboxylic Acid (24). To a 100 L four-neck round-
bottom flask equipped with an overhead stirrer, a thermocouple, and a
nitrogen inlet were charged compound 20 (2.920 kg, 3.980 mol), THF
(40 L), Et3N (1.660 L, 11.94 mol), 10 wt % of 10 wt % wet Pd/C
(0.292 kg), formic acid (0.450 L, 11.94 mol), and then THF (4 L for
the rinse). The mixture was heated to 50 °C over 0.5 h. After 0.5 h of
stirring at 50 °C for, an aliquot was removed and assayed by HPLC to
show no compound 20 remained.
The mixture was cooled to 25 °C and then filtered through a pad of
Solka Flock. The cake was washed with THF (10 L). The combined
filtrate and wash was transferred to a 100 L vessel, and then toluene
(29 L), water (8 L), and brine (8 L) were added. The mixture was
stirred for 0.5 h, and then a two-layer system was obtained. The
aqueous layer was cut and assayed by HPLC to show no amino acid
24. The organic layer was obtained and assayed by HPLC against to
standard to give amino acid 24 (2.520 kg, 98% HPLC yield). The
resulting organic solution was used for the next step.
A small amount of the crude product was purified by
chromatography on silica gel to afford pure amino acid 24 as white
solid, mp 241.5−242.3 °C. [α]20D −83.3° (MeOH, c = 1.0). 1H NMR
(400 MHz, CDCl3) δ: 6.12 (br s, 2 H), 5.75 (m, 1 H), 5.42 (br d, J =
5.2 Hz, 1 H), 3.72 (d, J = 10.2 Hz, 1 H), 3.70 (d, J = 11.6 Hz, 1 H),
3.46 (d, J = 10.2 Hz, 1 H), 3.45 (d, J = 11.7 Hz, 1 H), 3.37 (d, J = 11.6
Hz, 1 H), 3.30 (d, J = 11.7 Hz, 1 H), 3.14 (d, J = 8.8 Hz, 1 H), 2.73 (s,
1 H), 2.44 (dd, J = 13.3, 7.0 Hz, 1 H), 2.31 (s, 3 H), 2.20 (m, 1 H),
2.03 (s, 3 H), 2.00−1.95 (m, 3 H), 1.87 (m, 1 H), 1.80−1.630 (m, 4
H), 1.58−1.40 (m, 3 H), 1.39−1.27 (m, 2 H), 1.24 (s, 3 H), 1.23−1.19
(m, 5H), 1.15 (s, 3 H), 0.93 (d, J = 6.9 Hz, 3 H), 0.91 (d, J = 6.9 H, 3
H), 0.86 (d, J = 6.7 Hz, 3 H), 0.84 (s, 3 H), 0.82 (d, J = 6.7 Hz, 3 H),
0.74 (d, J = 7.1 Hz, 3 H), 0.71 (s, 3 H). 13C NMR (100 MHz, CDCl3)
δ: 178.5, 170.2, 141.0, 121.2, 87.0, 76.1, 75.2, 72.4, 67.7, 65.8, 53.4,
47.8, 44.5, 40.4, 40.3, 40.0, 39.8, 38.3, 37.7, 37.6, 31.6, 29.2, 28.1, 27.0,
26.5, 24.9, 21.9, 21.7, 21.5, 20.6, 19.3, 18.5, 18.0, 17.9, 17.7, 17.2, 16.8,
15.8, 8.1. HRMS (ESI) calculated for C39H65NO6: 644.4885 (M +
H)+, found 644.4882. Anal. Calcd for C39H65NO6: C, 72.74; H, 10.17;
N: 2.18. Found: C, 72.42; H, 10.24; N: 2.14.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-3-Acetoxy-2-((S)-
2-(((benzyloxy)carbonyl)(methyl)amino)-2,3-dimethylbutoxy)-
1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-1,4a-
(methanooxymethano)chrysene-7-carboxylic Acid (22). To a
100 L four-neck round-bottom flask equipped with an overhead stirrer,
a thermocouple, and a nitrogen inlet were charged amino-acid 24
(2.520 kg, 3.910 mol), THF (10 L), toluene (2.5 L), 20 wt % K2CO3
(7.00 L, 11.73 mol), and CbzCl (1.450 L, 9.780 mol). THF (2.6 L)
was used to rinse. The mixture was stirred at 20 °C for 3 h.
was then added, and the layers were separated. The organic layer was
concentrated and solvent-switch to toluene (8.4 L, total vol).
Next, cyclohexane (30 L) was added. The resulting solution was
washed by DMSO/water (5:1, 10.8 L × 3). At this point, the benzyl
alcohol byproduct was completely washed out. The organic solution
was washed by water (14.4 L × 3) to remove all DMSO. Assay
product in the organic solution by HPLC against standard was 2.980
kg (98% HPLC yield overall).
The organic solution was concentrated and solvent-switched to
dichloromethane (48 L, total volume) which contains N-Cbz acid 22
(2.980 kg, c = 0.0621 kg/L). At this point, the ratio of product with
toluene was 1:1.87 (mol ratio). There was no cyclohexane in the
solution. The resulting dichloromethane solution was used for the
ketene formation.
A small amount of the crude product 22 was purified by Biotage
(eluting with hexanes/EtOAc = 100:0 to 75:25) to afford pure N-Cbz
acid 22 as white solid, mp 150.1−151.0 °C. [α]20D −75.3° (CHCl3, c =
1.0). 1H NMR (400 MHz, CDCl3) δ: 10.96 (br s, 1 H), 7.35−7.26 (m,
5 H), 5.67 (m, 1 H), 5.43 (m, 1 H), 5.10 (d, J = 12.5 Hz, 1 H), 4.98
(d, J = 12.5 Hz, 1 H), 4.38 (m, 1 H), 3.72 (d, J = 11.6 Hz, 1 H), 3.49
(d, J = 11.4 Hz, 1 H), 3.43 (d, J = 8.5 Hz, 1 H), 3.36 (d, J = 11.4 Hz, 1
H), 3.28 (d, J = 11.6 Hz, 1 H), 2.99 (d, J = 9.2 Hz, 1 H), 2.96 (s, 3 H),
2.83 (s, 1 H), 2.80 (m, 1 H), 2.46 (dd, J = 13.1, 7.6 Hz, 1 H), 2.14 (m,
1 H), 2.06 (s, 3 H), 2.02−1.89 (m, 2 H), 1.78−1.68 (m, 3 H), 1.62−
1.34 (m, 5 H), 1.28 (s, 3 H), 1.26−1.20 (m, 4 H), 1.18 (s, 3 H), 1.13
(s, 3 H), 0.88 (d, J = 6.6 Hz, 3 H), 0.83 (d, J = 6.7 Hz, 3 H), 0.81 (d, J
= 6.8 Hz, 6 H), 0.75 (d, J = 6.7 Hz, 3 H), 0.74 (s, 3 H), 0.71 (s, 3 H).
13C NMR (100 MHz, CDCl3) δ: 179.5, 170.7, 155.7, 141.2, 137.3,
128.3 (2 C), 127.8 (2 C), 127.6, 120.5, 86.0, 76.6, 75.8, 72.1, 66.3,
65.8, 64.5, 52.3, 48.0, 44.5, 40.6, 40.3, 39.9, 39.6, 38.5, 37.7, 37.4, 37.1,
33.4, 30.7, 28.9, 27.8, 26.4, 24.8, 21.7, 20.4, 19.0, 18.4, 18.3, 17.8, 17.7,
17.2 (2 C), 16.4, 15.6, 8.1. HRMS (ESI) calculated for C47H71NO8:
778.5252 (M + H)+, found 778.5245. Anal. Calcd for C47H71NO8: C,
72.55; H, 9.20; N: 1.80. Found: C, 72.63; H, 9.21; N: 1.70.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-2-((S)-2-
(((Benzyloxy)carbonyl)(methyl)amino)-2,3-dimethylbutoxy)-7-
carbamoyl-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-1,4a-
(methanooxymethano)chrysen-3-yl Acetate (8). To a 100 L
four-neck round-bottom flask equipped with an overhead stirrer, a
thermocouple, a condenser and a nitrogen inlet was charged 1.520 kg
of N-Cbz acid 22 (1.960 mol) in dichloromethane solution (25.45 L, c
= 0.06201 kg/L). EDC (1.880 kg, 9.800 mol) was added, and the
mixture was aged at 35 °C overnight. Heating was stopped, and the
reaction mixture was washed with 5% brine solution (25 L × 1). The
organic layer was collected and assayed by HPLC against to pure
standard to give ketene 26 (1.262 kg, 100% HPLC yield). The ketene
dichloromethane solution was solvent-switched to toluene (12 L, total
vol), and the resulting solution was used in the next step.
A small amount of the solution was purified by Biotage (eluting
with heptanes/EtOAc = 100:0 to 60:40) to obtain pure ketene 26, mp
1
152.7−153.6 °C. [α]20 −76.6° (MeOH, c = 1.0). H NMR (400
MHz, CDCl3) δ: 7.38−D7.28 (m, 5 H), 5.70 (m, 1 H), 5.47 (m, 1 H),
5.12 (d, J = 12.5 Hz, 1 H), 5.00 (d, J = 12.5 Hz, 1 H), 4.41 (br d, J =
7.4 Hz, 1 H), 3.72 (d, J = 11.6 Hz, 1 H), 3.52 (d, J = 11.5 Hz, 1 H),
3.37 (dd, J = 11.6, 1.8 Hz, 1 H), 3.29 (d, J = 11.5 Hz, 1 H), 3.00 (d, J =
8.7 Hz, 1 H), 2.97 (s, 3 H), 2.82 (m, 1 H), 2.47 (dd, J = 13.3, 7.1 Hz, 1
H), 2.19 (m, 1 H), 2.08 (s, 3 H), 1.93−1.82 (m, 2 H), 1.79−1.62 (m, 6
H), 1.53 (m, 1 H), 1.44−1−41 (m, 2 H), 1.30 (s, 3 H), 1.25−1.15 (m,
10 H), 0.90 (d, J = 6.9 Hz, 3 H), 0.88 (d, J = 6.7 Hz, 3 H), 0.84 (d, J =
6.7 Hz, 3 H), 0.82 (d, J = 6.5 Hz, 6 H), 0.77 (s, 3 H), 0.72 (s, 3 H).
13C NMR (100 MHz, CDCl3) δ: 203.2, 170.6, 155.8, 141.6, 137.5,
128.4 (2 C), 127.9 (2 C), 127.7, 123.4, 120.1, 86.2, 76.8, 75.8, 72.1,
67.2, 66.4, 65.9, 64.6, 48.2, 46.9, 44.8, 40.3, 40.0, 39.0, 38.9 (2 C), 36.4,
36.3, 36.1, 33.4, 30.8, 27.8, 27.7, 27.6, 27.5, 24.9, 24.6, 21.8, 18.9, 18.7,
17.9 (2 C), 17.3, 16.9, 8.7. HRMS (ESI) calculated for C47H69NO7:
777.5418 (M + NH4)+, found 777.5415.
Then, 5 N NaOH solution was slowly added, and the mixture was
stirred at 20 °C for 6 h. Five normal HCl was slowly added (gas
evolution) so that the pH of the aqueous was <4. Toluene (25.2 L)
In a 10 gallon Banco reactor was charged the above 12 L of toluene
solution of 1.262 kg of ketene. The solution was cooled to −10 °C,
and 6 L of liquid NH3 was added. The mixture was stirred at 40 °C
3306
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
and 190 psi for 24 h. After being cooled to 0 °C and slow careful
venting, the mixture was transferred to a 50 L cylinder vessel and
diluted with 16 L of toluene. The mixture was washed with DMSO/
water (5:1, 5 L × 6). To the organic layer was added 3 L of EtOAc,
and the mixture was then washed with water (5.5 L × 3). The organic
layer was concentrated to 3 volumes and flushed with 2 volumes of
toluene. Heptane (6 L) was added slowly, and the slurry was stirred for
at rt 1 h. The crystalline solid was collected by filtration, washed with
heptane/toluene (3:1, 3 L × 1), and dried under vacuum with N2
sweep giving crystalline amide product 8 (1.356 kg, 89% isolated yield
from intermediate 22), mp 154.6−155.0 °C. [α]20D −76.6° (MeOH, c
= 1.0). 1H NMR (500 MHz, CDCl3) δ: 7.39−7.29 (m, 5 H), 5.70 (m,
1 H), 5.44 (s, 1 H), 5.37 (br s, 1 H), 5.33 (br s, 1 H), 5.13 (d, J = 12.5
Hz, 1 H), 5.01 (d, J = 12.5 Hz, 1 H), 4.40 (d, J = 5.7 Hz, 1 H), 3.74 (d,
J = 11.6 Hz, 1 H), 3.50 (d, J = 11.5 Hz, 1 H), 3.46 (d, J = 8.6 Hz, 1 H),
3.38 (d, J = 11.5 Hz, 1 H), 3.30 (d, J = 11.6 Hz, 1 H), 3.02 (d, J = 8.6
Hz, 1 H), 2.99 (s, 3 H), 2.83 (m, 1 H), 2.50 (s, 1 H), 2.48 (dd, J =
13.3, 7.1 Hz, 1 H), 2.10 (s, 3 H), 2.08−2.04 (m, 2 H), 1.82−1.68 (m, 6
H), 1.61−1.44 (m, 3 H), 1.39−1.35 (m, 2 H), 1.31 (s, 3 H), 1.29−1.24
(m, 5 H), 1.22 (s, 3 H), 0.95 (d, J = 6.8 Hz, 3 H), 0.88 (d, J = 6.5 Hz, 3
H), 0.84 (d, J = 6.8 Hz, 6 H), 0.79 (d, J = 6.7 Hz, 3 H), 0.78 (s, 3 H),
0.73 (s, 3 H). 13C NMR (100 MHz, CDCl3) δ: 175.8, 170.9, 155.8,
141.6, 137.5, 128.4 (2C), 127.8 (2 C), 127.7, 120.5, 86.1, 76.7, 75.9,
72.4, 66.4, 65.9, 64.6, 52.7, 47.0, 44.5, 41.0, 40.3, 40.0, 39.7, 38.6, 37.9,
37.7, 37.6, 33.4, 30.9, 28.8, 27.8, 26.8, 24.9, 21.8, 20.7, 19.1, 18.7, 18.5,
17.9, 17.8, 17.4, 17.3, 16.1, 15.8, 8.3. HRMS (ESI) calculated for
C47H72N2O7: 777.5412 (M + H)+, found 777.5418. Anal. Calcd for
C47H72N2O7: C, 72.64; H, 9.34; N: 3.60. Found: C, 72.98; H, 9.48; N:
3.43.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-2-((S)-2-
(((Benzyloxy)carbonyl)(methyl)amino)-2,3-dimethylbutoxy)-7-
carbamoyl-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
6-oxo-2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-
1H-1,4a-(methanooxymethano)chrysen-3-yl Acetate (9). To a
50 L cylinder vessel, equipped with an overhead stirrer, thermocouple,
dropping funnel, and nitrogen inlet were charged dichloromethane
(19.5 L) and amide 8 (1.158 kg, 1.489 mol), and the mixture was
cooled to 0−5 °C. To the resulting solution was added 37 wt %
Pd(OH)2/C (0.0567 kg, 10 mol %) and potassium carbonate powder
(0.031 kg, 15 mol %), respectively. Cumene hydroperoxide (CHP, 88
wt %, 1.489 L, 6 equiv) was added, and the reaction mixture was aged
at 0−5 °C for 22 h.
Five mole percent of 37 wt % Pd(OH)2/C (0.0283 kg) and another
portion of cumene hydroperoxide (1.489 L, 6 equiv) was added and
aged at the same temperature for 23 h. Then, 5.0 M TBHP in decane
(1.49 L, 5 equiv) was added, and the solution was stirred at 0−5 °C for
23 h. Then, another 5 equiv of 5.0 M of TBHP (1.47 L) was added
and aged for another 30 h. The third 5 equiv of 0.5 M TBHP (5 M,
1.47 L) was added and stirred at the same temperature for 23 h (>97%
conversion).
The catalyst was filtered off and washed by methylene chloride
(64% HPLC yield against to standard). The filtrate was solvent-
switched to MeOH (12 L, total vol) at <10 °C, and 12 L of MeOH
was added to the 50 L round-bottom before starting the solvent-
switch.
The resulting methanol solution was slowly added to a 25 wt %
Na2S2O3 (47 L) aqueous solution until the excess oxidant has been
quenched. The reaction mixture was extracted by toluene (12 L × 2).
The combined organic layer was washed by 16% brine (6 L × 1). The
organic layer was concentrated and solvent-switched to heptane (5.1 L,
0.754 kg of desired product 9 assayed by HPLC against to standard).
The crude product was purified by Biotage (eluting with heptanes/
EtOAc = 100:0 to 2:1), and then further purified by reverse phase
HPLC separation to give desired product N-Cbz enone amide 9
J = 11.5 Hz, 1 H), 3.30 (d, J = 11.7 Hz, 1 H), 3.23 (s, 1 H), 3.04 (d, J =
8.3 Hz, 1 H), 2.98 (s, 3 H), 2.83 (m, 1 H), 2.56−2.48 (m, 2 H), 2.10
(s, 3 H), 2.05 (m, 1 H), 1.90−1.80 (m, 2 H), 1.74−1.67 (m, 6 H),
1.65−1.48 (m, 4 H), 1.37−1.26 (m, 5 H), 1.21 (s, 3 H), 0.99 (d, J =
6.6 Hz, 3 H), 0.88 (d, J = 6.4 Hz, 3 H), 0.84 (d, J = 6.8 Hz, 6 H), 0.81
(s, 3 H), 0.78 (s, 3 H), 0.77 (d, J = 7.0 Hz, 3 H). 13C NMR (100 MHz,
CDCl3) δ: 205.1, 176.9, 170.4, 161.4, 155.2, 137.3, 128.3 (2 C), 127.7
(2 C), 127.5, 123.2, 85.6, 76.7, 75.0, 70.8, 66.3, 65.8, 64.4, 52.1, 49.3,
45.2, 44.7, 43.0, 42.3, 41.4, 40.8, 40.7, 39.9, 38.1, 33.3, 30.7, 27.4, 26.9,
26.7, 26.5, 24.4, 22.1, 21.6, 28.8, 18.6, 17.9, 17.8, 17.6, 17.1, 16.2, 16.0.
HRMS (ESI) calculated for C47H70N2O8: 808.5473 (M + NH4)+,
found 808.5476. Anal. Calcd for C47H70N2O8: C, 71.36; H, 8.92; N:
3.54. Found: C, 71.09; H, 8.93; N: 3.27.
(1S,2R,3R,4aR,6R,6aS,7R,8R,10aR,10bR,12aR)-2-((S)-2-
(((Benzyloxy)carbonyl)(methyl)amino)-2,3-dimethylbutoxy)-7-
carbamoyl-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
6-((2-phenylpropan-2-yl)peroxy)-2,3,4,6,6a,7,8,9,10,10a,-
10b,11,12,12a-tetradecahydro-1H-1,4a-(methanooxy-
methano)chrysen-3-yl Acetate (30). White solid, mp 129.5−130.3
°C. [α]25D −71.5° (MeOH, c = 0.33). 1H NMR (500 MHz, CDCl3) δ:
7.43−7.26 (m, 10 H), 5.83 (dd, J = 5.2, 2.1 Hz, 1 H), 5.74−5.69 (m, 2
H), 5.11 (m, 1 H), 5.02−4.98 (m, 2 H), 4.40 (m, 1 H), 3.80 (d, J = 5.2
Hz, 1 H), 3.75 (d, J = 11.6 Hz, 1 H), 3.53 (d, J = 12.0 Hz, 1 H), 3.44
(d, J = 8.6 Hz, 1 H), 3.39 (dd, J = 11.6, 2.1 Hz, 1 H), 3.29 (d, J = 12.0
Hz, 1 H), 3.21 (s, 1 H), 3.00 (d, J = 9.2 Hz, 1 H), 2.98 (s, 3 H), 2.81
(m, 1 H), 2.71 (s, 1 H), 2.52 (dd, J = 13.4, 7.5 Hz, 1 H), 2.09 (s, 3 H),
2.01 (d, J = 12.6 Hz, 1 H), 1.81−1.67 (m, 3 H), 1.61 (m, 1 H), 1.55 (s,
3 H), 1.49 (m, 1 H), 1.40−1.36 (m, 2 H), 1.30 (s, 3 H), 1.28−1.23 (m,
3 H), 1.22 (s, 3 H), 1.19 (s, 3 H), 1.15 (s, 3 H), 1.05 (m, 1 H), 0.82
(d, J = 7.0 Hz, 6 H), 0.78 (d, J = 7.2 Hz, 3 H), 0.76 (s, 3 H), 0.73 (d, J
= 6.8 Hz, 3 H), 0.66 (d, J = 7.4 Hz, 3 H), 0.61 (s, 3 H). 13C NMR
(125 MHz, CDCl3) δ: 175.9, 170.4, 155.8, 144.6, 144.4, 137.4, 128.4
(2 C), 128.1 (2 C), 127.8 (2 C), 127.6 (2 C), 125.7 (2 C), 119.3, 85.9,
81.8, 81.1, 77.3, 75.7, 71.7, 66.4, 65.9, 64.6, 46.4, 44.8, 44.4, 43.2, 40.6,
40.3, 40.2, 40.1, 38.4, 36.8, 33.4, 30.8, 28.7, 28.2, 27.0, 26.8, 26.5, 25.7,
24.9, 22.0, 21.8, 19.0, 18.9, 18.6, 18.5, 17.9, 17.7, 17.6, 17.2, 7.8. HRMS
(ESI) calculated for C56H82N2O8: 911.6144 (M + H)+, found
911.6153.
(1S,2R,3R,4aR,6R,6aS,7R,8R,10aR,10bR,12aR)-2-((S)-2-
(((Benzyloxy)carbonyl)(methyl)amino)-2,3-dimethylbutoxy)-6-
(tert-butylperoxy)-7-carbamoyl-1,6a,8,10a-tetramethyl-8-((R)-
3-methylbutan-2-yl)-2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tet-
radecahydro-1H-1,4a-(methanooxymethano)chrysen-3-yl Ace-
tate (27). White solid, mp 135.0−135.8 °C. [α]25D −89.5° (MeOH, c
= 1.0). 1H NMR (500 MHz, CDCl3) δ: 7.38−7.30 (m, 4 H), 7.28 (m,
1 H), 6.49 (s, 1 H), 5.80 (dd, J = 5.2, 2.1 Hz, 1 H), 5.70 (m, 1 H), 5.31
(s, 1 H), 5.12 (d, J = 12.4 Hz, 1 H), 4.98 (d, J = 12.4 Hz, 1 H), 4.40
(m, 1 H), 3.79 (d, J = 5.2 Hz, 1 H), 3.73 (d, J = 12.0 Hz, 1 H), 3.50 (d,
J = 11.7 Hz, 1 H), 3.42 (d, J = 9.0 Hz, 1 H), 3.38 (dd, J = 12.0, 2.1 Hz,
1 H), 3.27 (d, J = 11.7 Hz, 1 H), 3.13 (s, 1 H), 2.99 (d, J = 9.0 Hz, 1
H), 2.96 (s, 3 H), 2.80 (m, 1 H), 2.50 (dd, J = 13.4, 7.5 Hz, 1 H), 2.08
(s, 3 H), 2.05 (m, 2 H), 1.81−1.67 (m, 3 H), 1.53−1.40 (m, 4 H), 1.34
(m, 1 H), 1.32 (s, 3 H), 1.28 (s, 3 H), 1.26−1.22 (m, 2 H), 1.20 (s, 9
H), 1.17 (s, 3 H), 1.13 (m, 1 H), 0.91 (d, J = 7.3 Hz, 3 H), 0.83 (d, J =
6.8 Hz, 3 H), 0.81 (d, J = 7.3 Hz, 6 H), 0.80 (s, 3 H), 0.76 (s, 3 H),
0.74 (d, J = 7.5 Hz, 3 H). 13C NMR (125 MHz, CDCl3) δ: 176.7,
170.7, 155.7, 144.6, 137.4, 128.4 (2 C), 127.8 (2 C), 127.6, 119.9, 85.9,
81.2, 80.0, 76.7, 75.7, 71.6, 66.4, 65.9, 64.7, 47.0, 45.5, 44.4, 43.2, 40.7,
40.4, 40.2, 40.1, 38.4, 36.9, 33.4, 30.8, 28.8, 28.7, 27.0, 26.7 (3 C), 24.8,
21.9, 21.8, 19.0, 18.9, 18.6 (2 C), 17.9, 17.8, 17.7, 17.2 (2 C), 8.1.
HRMS (ESI) calculated for C51H80N2O8: 849.5987 (M + H)+, found
849.5980.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-3-Acetoxy-2-((S)-
2-(((benzyloxy)carbonyl)(methyl)amino)-2,3-dimethylbutoxy)-
1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-6-oxo-
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-1,4a-
(methanooxymethano)chrysene-7-carboxylic Acid (10). To a
50 L 4-neck round-bottom, equipped with an overhead stirrer,
thermocouple, and nitrogen inlet were charged acetonitrile (15.0 L),
enone amide 9 (0.6904 kg, 0.8727 mol), and water (0.300 L), and the
mixture was warmed to 28 °C. To the resulting solution was slowly
(0.573 kg, 49% isolated yield from intermediate 8) as white solid, mp
1
152.2−153.3 °C. [α]20 −54.3° (CHCl3, c = 1.0). H NMR (500
D
MHz, CDCl3) δ: 7.39−7.30 (m, 5 H), 6.12 (br s, 1 H), 5.75 (d, J = 1.4
Hz, 1 H), 5.73 (m, 1 H), 5.25 (br s, 1 H), 5.13 (d, J = 12.5 Hz, 1 H),
5.01 (d, J = 12.5 Hz, 1 H), 4.45 (d, J = 6.4 Hz, 1 H), 3.79 (d, J = 11.7
Hz, 1 H), 3.56 (d, J = 11.5 Hz, 1 H), 3.46 (d, J = 8.3 Hz, 1 H), 3.41 (d,
3307
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
added 90 wt % tert-butyl nitrite (0.576 L, 5.00 equiv) at 28−35 °C
(exothermic reaction), and the mixture was stirred at 28−35 °C for
0.5−1 h (typical >99% conversion).
L four-neck round-bottom flask equipped with an overhead stirrer, a
thermocouple, and a nitrogen inlet, was charged acetate salt (1)
(0.3200 kg, 0.4410 mol) and MeCN/MeOH (5:1, 3.2 L). Then, acetic
acid was added dropwise, and 37% formaldehyde aqueous solution
(1.616 L, 11.03 mol) was added slowly. The reaction mixture was
cooled to 15 °C, and then solid sodium cyanoborohydride (0.0550 kg,
0.8820 mol) was added in portions to maintain the internal
temperature <20 °C. The reaction mixture was heterogeneous
solution. The reaction mixture was stirred at rt for 20 h (100%
conversion).
The reaction mixture was concentrated to 3.75 L (total volume),
and EtOAc (12 L) was added. The resulting solution was washed with
10% NaHCO3 (4.5 L), water (4.5 L), and brine (4.5 L). The organic
layer was concentrated and completely solvent-switched to acetonitrile
(5.8 L, total volume). At this point, small amount of crystalline solid
N-Cbz enone acid 10 was formed. The resulting slurry was stirred at
0−5 °C for 16 h. The crystalline solid was collected by filtration, rinsed
by cold acetonitrile (0 °C), and dried under vacuum with nitrogen
sweep to afford crystalline N-Cbz enone acid 10 (0.491 kg, 83%
isolated yield) as colorless needles, mp 223.5−224.0 °C. [α]20D −66.2°
The reaction mixture was concentrated and solvent-switched to
ethyl acetate (12 L, total vol). The resulting solution was washed by 5
wt % sodium bicarbonate (4.8 L × 2) and water (3.2 L × 4). The
organic layer was concentrated and solvent-switched to IPA (1.92 L,
total volume). Crystalline solid 2 was formed during the solvent-
switch. Water (3.2 L) was slowly added over 1.5 h. The resulting slurry
was aged at rt for 2 h. The crystalline solid was collected by filtration,
washed by water/IPA (2:1, 1 L), and dried under vacuum with
nitrogen sweep to afford crystalline free base 2 as colorless needles
1
(CHCl3, c = 1.0). H NMR (500 MHz, CDCl3) δ: 8.61 (br s, 1 H),
7.39−7.28 (m, 5 H), 5.83 (d, J = 2.2 Hz, 1 H), 5.73 (m, 1 H), 5.13 (d,
J = 12.5 Hz, 1 H), 5.01 (d, J = 12.5 Hz, 1 H), 4.45 (d, J = 6.5 Hz, 1 H),
3.79 (d, J = 11.7 Hz, 1 H), 3.58 (d, J = 11.4 Hz, 1 H), 3.47 (d, J = 8.5
Hz, 1 H), 3.44 (d, J = 12.5 Hz, 1 H), 3.31 (d, J = 11.7 Hz, 1 H), 3.20
(s, 1 H), 3.04 (d, J = 8.5 Hz, 1 H), 2.99 (s, 3 H), 2.83 (m, 1 H), 2.56−
2.50 (m, 2 H), 2.20 (m, 1 H), 2.10 (s, 3 H), 1.91−1.83 (m, 3 H),
1.74−1.54 (m, 6 H), 1.52−1.48 (m, 2 H), 1.37−1.27 (m, 6 H), 1.16
(s, 3 H), 0.98 (d, J = 6.7 Hz, 3 H), 0.87 (d, J = 6.6 Hz, 3 H), 0.84 (d, J
= 6.9 Hz, 6 H), 0.81 (s, 6 H), 0.79 (d, J = 7.2 Hz, 3 H). 13C NMR
(100 MHz, CDCl3) δ: 203.7, 177.2, 170.5, 162.3, 155.8, 137.4, 128.4
(2 C), 127.9 (2 C), 127.7, 123.1, 85.8, 76.9, 75.1, 70.8, 66.5, 66.0, 64.7,
52.3, 46.0, 44.7, 43.3, 42.0, 41.3, 41.0, 40.9, 40.0, 38.2, 33.4, 30.8, 27.2,
26.7 (2 C), 24.5, 21.8, 21.7, 21.6, 18.8, 18.7, 18.2, 17.9, 17.8, 17.3, 16.0,
15.6, 8.1. HRMS (ESI) calculated for C47H69NO9: 792.5045 (M +
H)+, found 792.5038. Anal. Calcd for C47H69NO9: C, 71.27; H, 8.78;
N: 1.77. Found: C, 71.13; H, 9.00; N: 1.80.
(S)-1-(((1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-3-Acetoxy-
7-carboxy-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
6-oxo-2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-
1H-1,4a-(methanooxymethano)chrysen-2-yl)oxy)-N,2,3-trime-
thylbutan-2-aminium Acetate (1). To a 5 gallon vessel equipped
with an overhead stirrer and thermocouple was charged enone acid 10
(0.6887 kg, 0.8838 mol) in EtOAc (5.20 L) and methanol (5.20 L).
Twenty weight percent Pd(OH)2/C (0.0344 kg, 5% mol) and acetic
acid (0.146 L, 2.652 mol) were added, respectively. The resulting
reaction mixture was hydrogened under 40 psi of H2 at rt for 0.5−1 h
(100% conversion).
(0.267 kg, 90% yield), mp 217.0−218.0 °C. [α]20 −90.3° (MeOH, c
D
= 1.0). 1H NMR (500 MHz, CDCl3) δ: 5.82 (s, 1 H), 5.73 (m, 1 H),
3.82 (d, J = 11.7 Hz, 1 H), 3.72 (d, J = 9.6 Hz, 1 H), 3.57 (d, J = 11.5
Hz, 1 H), 3.53 (d, J = 9.6 Hz, 1 H), 3.43 (d, J = 11.5 Hz, 1 H), 3.31 (d,
J = 11.7 Hz, 1 H), 3.17 (s, 1H), 3.01 (d, J = 8.6 Hz, 1 H), 2.59−2.50
(m, 2 H), 2.36 (s, 6 H), 2.22 (m, 1 H), 2.09 (m, 1 H), 2.04 (s, 3 H),
1.90−1.81 (m, 3 H), 1.73−1.58 (m, 6 H), 1.55−1.48 (m, 2 H), 1.36−
1.29 (m, 3 H), 1.14 (s, 3 H), 0.96 (d, J = 6.6 Hz, 3 H), 0.92 (s, 3 H),
0.91 (d, J = 6.5 Hz, 3 H), 0.88−0.86 (m, 9 H), 0.81 (s, 3H), 0.77 (d, J
= 7.1 Hz, 3 H). 13C NMR (100 MHz, DMSO-d6) δ: 203.6, 177.3,
170.2, 161.8, 123.2, 86.7, 75.7, 75.2, 70.9, 66.0, 62.2, 52.3, 45.8, 44.8,
43.3, 41.9, 41.2, 40.9, 40.8, 39.9, 39.1 (2C), 38.2, 30.4, 27.2, 26.7, 26.6,
25.4, 24.5, 21.9, 21.6, 18.9, 18.7, 18.2 (2 C), 17.3, 15.9, 15.6, 14.6, 8.1.
HRMS (ESI) calculated for C40H65NO7: 672.4834 (M + H)+, found
672.4839. Anal. Calcd for C40H65NO7: C, 71.50; H, 9.75; N: 2.08.
Found: C, 71.36; H, 9.92; N: 1.97.
(S)-1-(((1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-3-Acetoxy-
7-carboxy-1,6a,8,10a-tetramethyl-8-((R)-3-methylbutan-2-yl)-
6-oxo-2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-
1H-1,4a-(methanooxymethano)chrysen-2-yl)oxy)-N,2,3-trime-
thylbutan-2-aminium Chloride (31). To a 250 mL four-neck
round-bottom flask equipped with an overhead stirrer, a thermocou-
ple, a dropping funnel, and nitrogen inlet were charged acetate salt 1
(5.410 g, 7.535 mmol) and 1:1 acetonitrile/water (80 mL). Sodium
bicarbonate (0.6300 g, 7.535 mmol) in water (6.3 mL) was added
dropwise at room temperature. The reaction mixture was stirred at rt
for 2−3 h. EtOAc (100 mL) was charged. The phase was separated.
The organic layer was washed with brine (25 mL × 2). The organic
layer was concentrated, and water was azotropically removed (KF
<200 ppm) by EtOAc. The solution was adjusted to 65 mL (total vol)
with EtOAc. Acetonitrile (30 mL) was charged. To the resulting
solution was added dropwise 3.9 N HCl in IPA (2.03 mL, 7.917
mmol) over 1 h. When half of the HCl in IPA solution was charged,
the batch was seeded with crystalline 31 (20 mg). The resulting slurry
was stirred at rt for 3−4 h. The crystalline HCl salt 31 was collected by
filtration, rinsed with EtOAc, and dried under vacuum with nitrogen
sweep to afford 31 (4.96 g, 95% isolated yield). The single crystal 31
was grown from MeCN/MeOH/EtOAc = 6:1:4, mp 241.0−242.1 °C.
[α]25D −66.9° (MeOH, c = 1.0). 1H NMR (500 MHz, CDCl3) δ: 9.54
(br s, 1 H), 9.17 (br s, 2 H), 5.89 (d, J = 2.0 Hz, 1 H), 5.76 (m, 1 H),
3.89−3.74 (m, 3 H), 3.52 (d, J = 11.7 Hz, 1 H), 3.36 (d, J = 11.7 Hz, 1
H), 3.28 (d, J = 12.3 Hz, 1 H), 3.16 (s, 1 H), 3.12 (dd, J = 10.7, 9.8 Hz,
1 H), 2.68 (s, 3 H), 2.62 (m, 1 H), 2.50 (m, 1 H), 2.27−2.17 (m, 2 H),
2.06 (s, 3 H), 2.10−2.03 (overlapped, m, 1 H), 1.90−1.76 (m, 3 H),
1.65 (s, 3 H), 1.67−1.61 (overlapped, m, 1 H), 1.56 (m, 1 H), 1.52−
1.45 (m, 2 H), 1.31 (s, 3 H), 1.34−1.25 (m, 3 H), 1.11 (s, 3 H), 1.09
(d, J = 6.7 Hz, 3 H), 0.99 (d, J = 6.6 Hz, 3 H), 0.94 (d, J = 6.5 Hz, 3
H), 0.91 (s, 3 H), 0.84 (d, J = 6.6 Hz, 3 H), 0.79 (s, 3 H), 0.75 (d, J =
7.1 Hz, 3 H). 13C NMR (125 MHz, CDCl3) δ: 204.2, 176.3, 170.3,
162.2, 123.2, 87.3, 75.3, 74.2, 70.7, 65.8, 64.3, 52.2, 45.8, 44.4, 43.0,
42.0, 41.2, 40.9, 40.8, 39.9, 38.3, 29.5, 27.6, 27.1, 26.6 (2 C), 24.5, 21.8,
The catalyst was filtered off by passing Solka Flock, washed by
MeOH/EtOAc (1:1, 4.6 L). The combined filtrates (filtered through
in-line filter) were solvent-switched to EtOAc (6.2 L, total volume).
The product crystalline solid was formed during solvent-switched.
Acetic acid (0.0731 L, 1.5 equiv) was added. The slurry was stirred at
rt for 4 h. The crystalline solid was collected by filtration, washed by
EtOAc (2.5 L × 1), dried under vacuum with wet nitrogen sweep to
remove remaining EtOAc, and then dried nitrogen to afford crystalline
salt 1 as colorless needles (0.607 kg, 98% isolated yield), mp 190.5−
1
191.8 °C. [α]20 −101.8 (MeOH, c = 1.0). H NMR (500 MHz,
D
CDCl3) δ: 5.80 (s, 1 H), 5.77 (m, 1 H), 5.48 (br s, 3 H), 3.78 (d, J =
9.0 Hz, 1 H), 3.77 (d, J = 11.9 Hz, 1 H), 3.61 (d, J = 9.7 Hz, 1 H), 3.54
(d, J = 11.3 Hz, 1 H), 3.44 (d, J = 11.3 Hz, 1 H), 3.31 (d, J = 11.9 Hz,
1 H), 3.15 (s, 1H), 3.07 (d, J = 9.0 Hz, 1 H), 2.54−2.50 (m, 2 H), 2.48
(s, 3 H), 2.23 (m, 1 H), 2.07 (s, 3 H), 2.02 (s, 3 H), 1.99 (m, 1 H),
1.91−1.85 (m, 3 H), 1.73−1.65 (m, 5 H), 1.59−1.49 (m, 3 H), 1.34−
1.24 (m, 3 H), 1.14 (s, 3 H), 1.12 (s, 3 H), 1.00−0.95 (m, 9 H), 0.88
(s, 3 H), 0.87 (d, J = 6.9 Hz, 3 H), 0.81 (s, 3 H), 1.55 (d, J = 7.1 Hz, 3
H). 13C NMR (100 MHz, CDCl3) δ: 204.0, 176.2, 173.6, 171.1, 164.2,
123.1, 86.8, 76.0, 75.8, 71.1, 66.4, 59.1, 52.6, 46.3, 45.1, 43.8, 42.3,
41.7, 41.6, 38.1, 32.5, 29.0, 27.6, 27.3, 27.1, 25.5, 22.9, 22.6, 22.5, 19.8,
19.2, 18.8, 18.5, 18.4, 18.2, 18.1, 16.6, 16.1, 9.1. HRMS (ESI)
calculated for C39H63NO7 [free amino acid, (M + H)+]: 658.4677,
found 658.4683. Anal. Calcd for C41H67NO9: C, 68.59; H, 9.41; N:
1.95. Found: C, 68.27; H, 9.68; N: 1.86.
(1S,2R,3R,4aR,6aS,7R,8R,10aR,10bR,12aR)-3-Acetoxy-2-((S)-
2-(dimethylamino)-2,3-dimethylbutoxy)-1,6a,8,10a-tetrameth-
y l - 8 - ( ( R ) - 3 - m e t h y l b u t a n - 2 - y l ) - 6 - o x o -
2,3,4,6,6a,7,8,9,10,10a,10b,11,12,12a-tetradecahydro-1H-1,4a-
(methanooxymethano)chrysene-7-carboxylic Acid (2). To a 20
3308
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
21.7, 18.7 (2 C), 18.4, 18.3, 17.2, 17.0, 16.1, 16.0, 15.6, 8.1. HRMS
(ESI) calculated for C39H63NO7 [free amino acid, (M + H)+]:
658.4677, found 658.4671.
(3) Schwartz, R. E.; Smith, S. K.; Onishi, J. C.; Meinz, M.; Kurtz, M.;
Giacobbe, R. A.; Wilson, K. E.; Liesch, J.; Zink, D.; Horn, W.; Morris,
S.; Cabello, A.; Vicente, F. J. Am. Chem. Soc. 2000, 122, 4882−4886.
(4) (a) Pelaez, F.; Cabello, A.; Platas, G.; Diez, M. T.; Gonzalez del
Val, A.; Basilio, A.; Martan, I.; Vicente, F.; Bills, G. E.; Giacobbe, R. A.;
Schwartz, R. E.; Onish, J. C.; Meinz, M. S.; Abruzzo, G. K.; Flattery, A.
M.; Kong, L.; Kurtz, M. B. Systematic Appl. Microbiol. 2000, 23, 333−
43. (b) Onishi, J.; Meinz, M.; Thompson, J.; Curotto, J.; Dreikorn, S.;
Rosenbach, M.; Douglas, C.; Abruzzo, G.; Flattery, A.; Kong, L.;
Cabello, A.; Vicente, F.; Pelaez, F.; Diez, M. T.; Martin, I.; Bills, G.;
Giacobbe, R.; Dombrowski, A.; Schwartz, R.; Morris, S.; Harris, G.;
Tsipouras, A.; Wilson, K.; Kurtz, M. B. Antimicrob. Agents Chemother.
2000, 44, 368−77.
(5) (a) Greenlee, M. L.; Meng, D.; Mamai, A.; Fan, W.; Balkovec, J.
M.; Peel, M.; Li, K. Antifungal agents. PCT Int. Appl. WO
2007126900, 2007. (b) Balkovec, J. M.; Boufford, F. A.; Tsu, B.;
Dropinski, J.; Meng, D.; Greenlee, M. L.; Peel, M.; Fan, W.; Mamai,
A.; Liu, H.; Li, K. Antifungal agents. PCT Int. Appl. WO 2007127012,
2007. (c) Balkovec, J. M.; Siliphaivanh, P.; Bouffard, F. A.; Peel, M. R.;
Fan, W.; Mamai, A.; Dimick G.; Ray, S. M. Antifungal agents. PCT Int.
Appl. WO 2009045311, 2009.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
Copies of H NMR, 13C NMR spectra of new compounds,
Table 4, and X-ray crystallographic data for compound 31 in
CIF format (deposition code: CCDC 857543). This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: yongli_zhong@merck.com.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
(6) (a) Joshi, D. K.; Sutton, J. W.; Carver, S.; Blanchard, J. P. Org.
Process Res. Dev. 2005, 9, 997−1002. (b) Costanzo, M. J.; Patel, M. N.;
Petersen, K. A.; Vogt, P. F. Tetrahedron Let 2009, 50, 5463−5466.
(7) The main degradation byproduct was the corresponding 3-ketone
13.
■
We thank Dr. T. J. Novak for mass spectrometric assistance.
We also thank Dr. W. R. Leonard, Mr. D. W. Henderson, and
Mr. J. C. Liu for assistance with Biotage chromatographic
purification and HPLC separation.
REFERENCES
■
(1) For selected recent progress and reviews, see: (a) Bauer, M.;
Reinhart, K. Int. J. Med. Microbiol. 2010, 300, 411−413. (b) Cadwell,
K.; Patel, K. K.; Maloney, N. S.; Liu, T.-C.; Ng, A. C. Y.; Storer, C. E.;
Head, R. D.; Xavier, R.; Stappenbeck, T. S.; Virgin, H. W. Cell 2010,
141, 1135−1145. (c) Gullo, A.; Foti, A.; Murabito, P.; Li Volti, G.;
Astuto, M.; Stissi, C.; Rubulotta, F.; Sanfilippo, F.; Santonocito, C.;
Sganga, G.; Ristagno, G. Frontiers Biosci. 2010, E2, 906−911.
(d) Simon, N.; Decaudin, B.; Lannoy, D.; Odou, M. F.; De
Broucker, M.; Barthelemy, C.; Poret, E.; Dubreuil, L.; Odou, P.
Pulm. Pharmacol. Ther. 2010, 23, 324−326. (e) Yong, M. K.; Buising,
K. L.; Cheng, A. C.; Thursky, K. A. J. Antimicrob. Chemother. 2010, 65,
1062−1069. (f) Rubio-Terres, C.; Grau, S. Expert Opin. Ther. Pat.
2010, 11, 877−887. (g) Chalmers, J. D.; Al-Khairalla, M.; Short, P. M.;
Fardon, T. C.; Winter, J. H. J. Antimicrob. Chemother. 2010, 65, 608−
618. (h) Kinnebrew, M. A.; Ubeda, C.; Zenewicz, L. A.; Smith, N.;
Flavell, R. A.; Pamer, E. G. J. Infect. Dis. 2010, 201, 534−543. (i) Isaacs,
D. Curr. Opin. Infect. Dis. 2008, 21, 246−250. (j) Zotchev, S. B. Curr.
Med. Chem. 2003, 10, 211−223. (k) Shaw, Peter J. J. Antimicrob.
Chemother. 2002, 49, 63−67.
(2) For selected recent progress and reviews, see: (a) Swoboda, S.;
Lichtenstern, C.; Ober, M. C.; Taylor, L. A.; Stoerzinger, D.; Michel,
A.; Brobeil, A.; Mieth, M.; Hofer, S.; Sonntag, H.-G.; Hoppe-Tichy, T.;
Weigand, M. A. Chemotherapy (Basel, Switz.) 2009, 55, 418−424.
(b) Zhu, A.; Xu, L. Zhongguo Yaofang 2009, 20, 2047−2049.
(c) Hajare, A. A.; Mali, M. N.; Sarvagod, S.; Kurane, S.; Patwardhan,
S.; Dange, A. S. Asian J. Res. Chem 2009, 2, 213−219. (d) Maschmeyer,
G.; Calandra, T.; Singh, N.; Wiley, J.; Perfect, J. Med. Mycol. 2009, 47
(6), 571−583. (e) Aikawa, N.; Kusachi, S.; Oda, S.; Takesue, Y.;
Tanaka, H. J. Infect. Chemother. 2009, 15, 219−227. (f) Brueggemann,
R. J. M.; Alffenaar, J.-W. C.; Blijlevens, N. M. A.; Billaud, E. M.;
Kosterink, J. G. W.; Verweij, P. E.; Burger, D. M. Clin. Infect. Dis. 2009,
48, 1441−1458. (g) Cannon, R. D.; Lamping, E.; Holmes, A. R.;
Niimi, K.; Baret, P. V.; Keniya, M. V.; Tanabe, K.; Niimi, M.; Goffeau,
A.; Monk, B. C. Clin. Microbiol. Rev. 2009, 22, 291−321. (h) Damle, B.
D.; Dowell, J. A.; Walsky, R. L.; Weber, G. L.; Stogniew, M.; Inskeep,
P. B. Antimicrob. Agents Chemother. 2009, 53, 1149−1156. (i) Gautam,
P.; Shankar, J.; Madan, T.; Sirdeshmukh, R.; Sundaram, C. S.; Gade,
W. N.; Basir, S. F.; Sarma, P. U. Antimicrob. Agents Chemother. 2008,
52, 4220−4227. (j) Maschmeyer, G.; Haas, A. Future Microbiol. 2006,
1, 365−385.
(8) For example: methyl or benzyl esters of 12 can not be hydrolyzed
to the corresponding carboxylic acid 12 by typical conditions such as
LiOH, NaOH, or KOH in THF/water or MeOH/water.
(9) For a review, see: Melendez, R. E.; Lubell, W. D. Tetrahedron
2003, 59, 2581.
(10) Kuethe, J. T.; Gauthier, D. R. Jr.; Beutner, G. L.; Yasuda, N. J.
Org. Chem. 2007, 72, 7469−7472.
(11) For selected recent progress and reviews, see: (a) Zhao, Y.;
Yeung, Y.-Y. Org. Lett. 2010, 12, 2128−2131. (b) Jiang, D.; Mallat, T.;
Meier, D. M.; Urakawa, A.; Baiker, A. J. Catal. 2010, 270, 26−33.
(c) Li, Y.; Wu, X.; Lee, T. B.; Isbell, E. K.; Parish, E. J.; Gorden, A. E.
V. J. Org. Chem. 2010, 75, 1807−1810. (d) Yin, C.; Yang, Z.; Li, B.;
Zhang, F.; Wang, J.; Ou, E. Catal. Lett. 2009, 131, 440−443. (e) Tan,
Q.; Hayashi, M. Adv. Synth. Catal. 2008, 350, 2639−2644.
(f) McLaughlin, E. C.; Choi, H.; Wang, K.; Chiou, G.; Doyle, M. P.
J. Org. Chem. 2009, 74, 730−738. (g) Choi, H.; Doyle, M. P. Org. Lett.
2007, 9, 5349−5352. (h) McLaughlin, E. C.; Doyle, M. P. J. Org.
Chem. 2008, 73, 4317−4319. (i) Brasholz, M.; Reissig, H.-U. Synlett
2007, 1294−1298. (j) Salvador, J. A. R.; Silvestre, S. M.; Moreira, V.
M. Curr. Org. Chem. 2006, 10, 2227−2257. (k) Shing, T. K. M.; Yeung,
Y.-Y.; Su, P. L Org. Lett. 2006, 8, 3149−3151. (l) Fousteris, M. A.;
Koutsourea, A. I.; Nikolaropoulos, S. S.; Riahi, A.; Muzart, J. J. Mol.
Catal. A: Chem. 2006, 250, 70−74. (m) Salvador, J. A. R.; Silvestre, S.
M. Tetrahedron Lett. 2005, 46, 2581−2584. (n) Yu, J.-Q.; Corey, E. J. J.
Am. Chem. Soc. 2003, 125, 3232. (o) Yu, J.-Q.; Corey, E. J. Org. Lett.
2002, 4, 2727. (p) Catino, A. J.; Forslund, R. E.; Doyle, M. P. J. Am.
Chem. Soc. 2004, 126, 13622−13623. (q) Arsenou, E. S.; Koutsourea,
A. I.; Fousteris, M. A.; Nikolaropoulos, S. S. Steroids 2003, 68, 407.
(r) Humphyrey, J. M.; Liao, Y.; Ali, A.; Rein, T.; Wong, Y.-L.; Chen,
H.-J.; Courtney, A. K.; Martin, S. F. J. Am. Chem. Soc. 2002, 124, 8584.
(s) Martin, S. F.; Humphrey, J. M.; Ali, A.; Hillier, M. C. J. Am. Chem.
Soc. 1999, 121, 866. (t) Liu, J.; Wang, F.; Ma, Z.; Lin, J.; Gu, Z. Catal.
Commun. 2011, 15, 103−107. (u) Catir, M.; Kilic, H. Synlett 2010,
1319−1322. (v) The allylic oxidation of the benzyl ester 21, and acid
22 and was also screened in microscale format (∼400 reactions total, 2
3309
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310

The Journal of Organic Chemistry
Article
mg scale). Supported metals (Pd, Pt, Rh, Ru) and their associated
oxides were screened, along with salts of Mn, Ru, Cr, and Cu in
various oxidation states in combination with several oxidants (TBHP,
BzOOtBu, MnO2, BQ, O2), all arrayed against solvents of varying
polarity (e.g., heptane, Toluene, PhCF3, DCM, EtOAc, MeCN).
(12) Allylic oxidation for the model studies:
(13) It was noticed that ketene 26 is surprisingly stable and does not
react with alcohols even at elevated temperature. When the crude acid
22, containing 1 equiv of BnOH and some dibenzyl carbonate, was
treated with EDC, only the corresponding benzyl ester was isolated in
high yield. It is interesting to note that ketene 26 did not react with an
excess amount of benzyl alcohol even at elevated temperature. Since
the same EDC reaction with isolated acid 22 and Me17OH provided
the clean 17O labeled methyl ester, it was confirmed that an activated
carboxylic acid with EDC reacted with alcohol not due to activation of
alcohol. Thus, excess BnOH had to be removed from the crude acid
mixture prior to formation of ketene. We found that benzyl alcohol
could be removed completely by three DMSO/water (5:1) washes of
the reaction mixture in cyclohexane without any loss of compound 22.
Then, without any further purification, compound 22 in cyclohexane
was concentrated and the residue was dissolved in dichloromethane,
and then treated with EDC at 35 °C to generate ketene 26. The
ketene was subsequently reacted with excess ammonia in toluene in
the autoclave at 40 °C to afford colorless crystalline amide 8 in 89%
isolated yield.
(14) (a) Tang, Y.; Dong, Y.; Wang, X.; Sriraghavan, K.; Wood, J. K.;
Vennerstrom, J. L. J. Org. Chem. 2005, 70, 5103−5110. (b) Rigaudy, J.;
Chelu, G.; Cuong, N. K. J. Org. Chem. 1985, 50, 4474−4478.
(c) McLaughlin, E. C.; Choi, H.; Wang, K.; Chiou, G.; Doyle, M. P. J.
Org. Chem. 2009, 74, 730−738. (d) Ahn, Y. M.; Velde, D. G. V.;
Georg, G. I. J. Org. Chem. 2002, 67, 7140−7143. (e) Yoshida, J.;
Nakatani, S.; Sakaguchi, K.; Isoe, S. J. Org. Chem. 1989, 54, 3383−
3389. (f) Muzart, J. Tetrahedron Lett. 1986, 27, 3139−3142.
(15) Optimization for the palladium-mediated allylic oxidation of
amide 8 (for details, see the Supporting Information):
(16) The dihedral angle of the carbon−carbon double bond and the
carbonyl, C9−C11−C12−O5, is −168.2°. This deviation from 180° of
11.8° is somewhat larger than is commonly observed in similar
moieties in the Cambridge Structural Database (0° to 8°); however,
there are several similar structures that show deviations of up to 18°.
With this broad of a range of observations it is difficult to draw
conclusions about the significance, if any, of the twist in this torsion
angle away from 180°. We do note that this enone is not stable under
strong acidic or strong basic conditions.
(17) Greenlee, M. L.; Wilkening, R.; Apgar, J.; Wildonger, K. J.;
Meng, D.; Parker, D. L.; Mamai, A. Preparation of enfumafungin
aglycon derivatives as antifungal agents, PCT Int. Appl., 2010.
3310
dx.doi.org/10.1021/jo300046v | J. Org. Chem. 2012, 77, 3297−3310