Synthesis of eight stereoisomers of pochonicine: Nanomolar inhibition of β-N-acetylhexosaminidases

Article abstract of DOI:10.1021/jo401694e

Pochonicine, the first naturally occurring polyhydroxylated pyrrolizidine containing an acetamidomethyl group, which was isolated from Pochonia suchlasporia var. suchlasporia TAMA 87, together with its enantiomer and their C-1 and/or C-3 epimers, have been synthesized from the sugar-derived cyclic nitrones 9D and 9L, respectively. An in-depth NMR study showed that both the ¹H and ¹³C NMR spectra of the synthetic pochonicines (1D and 1L) matched very well with those of natural pochonicine in D₂O, which unequivocally determined the relative configuration of the natural product as 1D or 1L. In addition, comparison of the optical rotations of the synthetic pochonicines and that of the natural product, but more convincingly their glycosidase inhibition profiles, confirmed the absolute configuration of natural pochonicine as 1R,3S,5R,6R,7S,7aR. Thereby, the structure of natural pochonicine was unequivocally determined as (+)-(1R,3S,5R,6R,7S,7aR)-pochonicine (1D). Glycosidase inhibition experiments showed that natural pochonicine 1D and its epimers 2D, 3D, and 4D all are powerful inhibitors of hexosaminidases (five β-N-acetylglucosaminidases and two β-N-acetylgalactosaminidases) while their enantiomers 1L, 2L, 3L, and 4L are much weaker inhibitors of the same enzymes. (-)-3-epi-Pochonicine (2L) was found to be a potent and selective inhibitor of α-l-rhamnosidase. None of the compounds showed any inhibition of α-GalNAcase.

Full text of DOI:10.1021/jo401694e

Article
pubs.acs.org/joc
Synthesis of Eight Stereoisomers of Pochonicine: Nanomolar
Inhibition of β‑N‑Acetylhexosaminidases
Jian-She Zhu,†,# Shinpei Nakagawa, Wei Chen, Isao Adachi, Yue-Mei Jia, Xiang-Guo Hu,
§
‡
§
†
⊥
†
∥
⊥
∇
⊥
George W. J. Fleet, Francis X. Wilson, Teruhiko Nitoda, Graeme Horne, Renate van Well,
,
§
,†
Atsushi Kato,* and Chu-Yi Yu*
†Beijing National Laboratory of Molecular Science (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
‡
College of Chemistry and Chemical Engineering, Jiang Xi Normal University, Nanchang, Jiangxi 330022, China
§
Department of Hospital Pharmacy, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
∥
Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K.
⊥
Summit PLC, 85b Park Drive, Milton Park, Abingdon, Oxon OX14 4RY, U.K.
#
University of the Chinese Academy of Sciences, Beijing 100049, China
∇
Laboratory of Bioresources Chemistry, the Graduate School of Environmental and Life Science, Okayama University, 1-1-1
Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
*
S Supporting Information
ABSTRACT: Pochonicine, the first naturally occurring
polyhydroxylated pyrrolizidine containing an acetamidomethyl
group, which was isolated from Pochonia suchlasporia var.
suchlasporia TAMA 87, together with its enantiomer and their
C-1 and/or C-3 epimers, have been synthesized from the
sugar-derived cyclic nitrones 9D and 9L, respectively. An in-
1
13
depth NMR study showed that both the H and C NMR
spectra of the synthetic pochonicines (1D and 1L) matched
very well with those of natural pochonicine in D O, which
2
unequivocally determined the relative configuration of the
natural product as 1D or 1L. In addition, comparison of the
optical rotations of the synthetic pochonicines and that of the
natural product, but more convincingly their glycosidase inhibition profiles, confirmed the absolute configuration of natural
pochonicine as 1R,3S,5R,6R,7S,7aR. Thereby, the structure of natural pochonicine was unequivocally determined as
(
+)-(1R,3S,5R,6R,7S,7aR)-pochonicine (1D). Glycosidase inhibition experiments showed that natural pochonicine 1D and its
epimers 2D, 3D, and 4D all are powerful inhibitors of hexosaminidases (five β-N-acetylglucosaminidases and two β-N-
acetylgalactosaminidases) while their enantiomers 1L, 2L, 3L, and 4L are much weaker inhibitors of the same enzymes. (-)-3-epi-
Pochonicine (2L) was found to be a potent and selective inhibitor of α-L-rhamnosidase. None of the compounds showed any
inhibition of α-GalNAcase.
1
INTRODUCTION
87 by Nitoda and co-workers in 2009. Glycosidase inhibition
assays showed that it is a powerful inhibitor (with IC50 on the
nanomolar scale) against β-N-acetylglucosaminidases (β-
GlcNAcases) from various organisms, including insects, fungi,
mammals, and plants. Its inhibition potency is similar to that of
the known powerful β-GlcNAcase inhibitor nagstatin. Pocho-
nicine represents the first example of a naturally occurring
pyrrolizidine alkaloid with potent inhibition of β-GlcNAcases.
In fungi and insects, chitinase combined with β-GlcNAcase
hydrolyzes the polysaccharide chitin into the monosaccharide
β-GlcNAc; this process is known to be necessary for the normal
■
Pochonicine, the first naturally occurring polyhydroxylated
pyrrolizidine containing an acetamidomethyl group (Figure 1),
was isolated from Pochonia suchlasporia var. suchlasporia TAMA
Received: August 2, 2013
Published: September 13, 2013
Figure 1. Structure of (+)-pochonicine.
©
2013 American Chemical Society
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Figure 2. Retrosynthetic analysis of pochonicine.
growth of these organisms. Inhibitors of such enzymes are
potentially useful in the discovery of novel pesticides and
fungicides. Furthermore, in mammals, especially in humans, O-
exceptional inhibition of GlcNAcase. As has been reported in
many cases, the glycosidase inhibition profiles of the
enantiomers of many naturally occurring iminosugars are
strikingly different from those of the natural products. An
in-depth evaluation of the glycosidase inhibition of pochoni-
cine, its enantiomer, and their C-1 and/or C-3 epimers provides
a preliminary structure−activity relationship of pochonicine and
eight of its 64 stereoisomers and will allow the design and
synthesis of even more potent inhibitors.
2
11
linked β-N-acetylglucosaminidase (O-β-GlcNAcase, OGA)
plays an important role in the regulation of insulin signaling
3
and as a mediator of glucose toxicity. Therefore, specific
inhibitors of OGA have shown great promise in the treatment
4
5
of many diseases such as insulin resistance, type-II diabetes,
Alzheimer’s disease, and cancer metastasis.
6
7
The structure of pochonicine was originally proposed as
Herein we present our work on the synthesis of both
enantiomers of pochonicine and their C-1 and/or C-3 epimers,
(1R,3S,5S,6S,7R,7aS)-4L (Figure 1) on the basis of NOE
1
13
an in-depth study of their H and C NMR spectra, and the
glycosidase inhibition profiles of all these stereoisomers in the
hope of developing an efficient method for the synthesis of
pochonicine and its analogues.
correlations, but its absolute configuration was not determined.
Takahashi and co-workers have recently completed a synthesis
of the proposed structure of pochonicine and its C-1 and/or C-
3
epimers (i.e., compounds 1L, 2L, 3L, and 4L); this work
revised the relative configuration and determined the absolute
8
configuration as (1R,3S,5R,6R,7S,7aR)-1D (Figure 1). How-
RESULTS AND DISCUSSION
■
ever, a slight uncertainty in the determination of the relative
and absolute configurations of pochonicine remains. First, the
relative configuration of pochonicine was determined by
comparison of the H and C NMR spectra of compound
L with those of the natural sample of pochonicine. However,
Retrosynthetic Analysis. The retrosynthetic analysis of
pochonicine is depicted in Figure 2. In view of the cis
configuration between H-7 and H-7a and the trans config-
uration between H-5 and H-6 in pochonicine, it can be
envisaged that 1L and its C-1 and/or C-3 epimers could be
synthesized starting from the all-cis D-ribose-derived cyclic
1
13
1
1
13
the reported H and C NMR spectra of compound 1L were
similar but not identical to those of the natural sample of
pochonicine. Second, the absolute configuration of pochonicine
was determined by comparison of the optical rotation of
compound 1L and that of the natural sample of pochonicine.
Since the values of the optical rotation of the free bases are very
small and change around zero, the comparison of optical
rotations may not be helpful. The optical rotations of the
hydrogen chloride salts of compound 1L and the natural
sample of pochonicine were also compared. However, the
determination of absolute configurations via such kinds of
comparison is not definitive: while the sign of optical rotation
of the hydrogen chloride salt is often the same as that of the
corresponding free base for many iminosugar alkaloids, there
12
nitrone 9L having the required cis configuration between H-7
and H-7a. The key intermediate 12L, with a unique
acetamidomethyl group, could be synthesized by nucleophilic
anti addition of cyanide to cyclic nitrone 9L
reduction and acetylation. The intermediate 16L could be
derived from 12L through selective removal of the trityl
protecting group, oxidation of the hydroxymethyl group to the
aldehyde, and subsequent allylic addition. Finally, the second
pyrrolidine ring could be assembled through dihydroxylation of
9d,13
followed by
the allyl group followed by intramolecular S 2 substitution of
N
the secondary cyclic amine and the secondary hydroxyl group,
affording the desired target compound. The enantiomer 1D
would be formed from cyclic nitrone 9D via an identical
synthetic route.
9
are many with opposite specific roatations. Therefore, it was
necessary to make a further investigation to determine
unambiguously both the relative and absolute configurations
of pochonicine through the synthesis of both enantiomers of
pochonicine and their C-1 and/or C-3 epimers, followed by an
Preparation of Cyclic Nitrones 9L and 9D. The starting
materials, cyclic nitrones 9L and 9D, were prepared from D-
ribose and L-ribose, respectively, in 22−30% overall yield on
multigram scales by the known procedure (Scheme 1).
Synthesis of Both Enantiomers of Pochonicine and
Their C-1 and/or C-3 Epimers. From cyclic nitrone 9L, we
investigated the synthesis of 1L and its C-1 and/or C-3
epimers. Addition of trimethylsilyl cyanide to the all-cis cyclic
nitrone 9L provided hydroxylamine 10L in 96% yield as a
14
1
13
in-depth study of their H and C NMR spectra as well as an
examination of the glycosidase inhibition profiles of all these
isomers. In view of our continued interest in the synthesis and
10
glycosidase inhibition of iminosugars, pochonicine was an
intriguing challenge to us because of its novel structure and
1
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Scheme 1. Preparation of Cyclic Nitrones 9L and 9D
alcohol 13L. Although the yield was moderate, the reaction
could be carried out on a decagram scale, as needed for the
multistep synthesis. After oxidation of the unmasked primary
hydroxyl group in 13L with Dess−Martin periodinane (DMP),
the resulting aldehyde 14L was subjected to aqueous Luche-
type allylation to afford a separable mixture of two products,
the homoallylic alcohols 15aL (more polar) and 15bL (less
polar), in excellent total yield over the two steps (89%) with a
24
1
5aL:15bL ratio of 1.4:1, slightly favoring the desired
stereoisomer.
It is noteworthy that allylation of 14L by the usual Grignard
addition led to complicated results, with the major product (ca.
4
0% yield) being the homoallylic alcohol with loss of the acetyl
group. Unlike the normal aqueous Luche allylation, which can
usually be run easily at room temperature or below, the
allylation of 14L had to be carried out at elevated temperature
single diastereoisomer (Scheme 2). The excellent yield and
selectivity were consistent with that reported by Goti and co-
(
about 60 °C) with a large excess of zinc powder and allylic
Scheme 2. Synthesis of Homoallylic Alcohols 16L and 17L
bromide, reflecting the low reactivity of aldehyde 14L.
The structures of 15aL and 15bL were characterized by MS,
IR, and H and C NMR analysis. The configuration of the
newly formed stereocenter during the allylation was assigned
unambiguously by X-ray crystallographic analysis of 15bL
1
13
(
Figure 3). Acetylation of 15aL and 15bL with Ac O and
2
DMAP in pyridine gave the key acetylated intermediates 16L
and 17L in excellent yields (99% and 96%, respectively).
1
3a
workers. Reduction of both the cyano and hydroxylamine
13b
groups in 10L by Raney Ni-catalyzed hydrogenation and in
situ protection of the two amino groups with Boc O furnished
2
di-tert-butyl carbamate 11L in excellent yield (85−92%).
Deprotonation of 11L with lithium diisopropylamide (LDA)
at −78 °C followed by the addition of Ac O gave N-Boc-N-acyl
2
amine 12L in 80% yield. The conventional method for
15
acetylation (DMAP, Ac O, rt or reflux) was unsuccessful. It
2
Figure 3. Crystal structure of compound 15bL.
was necessary to introduce an acetyl group on this amino group
as a protecting group that is stable under the conditions for
removal of the Boc group at a later stage of the synthesis.
16
Dihydroxylation of 16L by OsO (cat.) and N-methylmor-
4
With the acetamidomethyl group installed, we then turned
our attention to the synthesis of the homoallylic alcohols 16L
and/or 17L (Scheme 2). As had been expected, the selective
removal of the trityl group proved to be a troublesome task
because of the disturbance of the other three acid-sensitive
protecting groups in 12L. After optimization of the reaction
conditions and screening of several reagent systems (e.g., Pd/
pholine N-oxide (NMO) in acetone resulted in an inseparable
mixture of epimeric diols. However, after selective protection of
the resulting primary hydroxyl group, the O-TBS ethers could
be separated by silica gel column chromatography to yield 18aL
and 18bL (1.2:1 favoring 18aL, 88% overall yield in two steps
starting from 16L; Scheme 3). The relative configuration of the
C-3 position in 18aL and 18bL could be deduced from NOE
experiments on the corresponding final pyrrolizidine alkaloids.
Mesylation of the remaining secondary hydroxyl group of 18aL
1
7
18
19
20
C−H , CH COOH, HCl/CH OH, CuSO4, CBr4/
2
3
3
2
1
22
CH OH, InBr /CH OH, etc.), it was found that the trityl
3
3
3
group could be selectively removed via treatment of 12L with
and 18bL under standard conditions (i.e., MsCl and Et N in
DCM) gave the desired products 20L and 21L in 92% and 93%
3
23
the HCOOH/Et O in 50−58% yield to give the desired
2
1
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Scheme 3. Synthesis of (−)-Pochonicine (1L) and (−)-3-epi-
Pochonicine (2L)
23L followed by cyclization under basic conditions yielded the
protected pyrrolidines 26L and 27L in moderate yields (43%
and 40%, respectively, over two steps). Global deprotection of
2
6L and 27L in acidic methanol provided the target
compounds 1-epi-pochonicine (3L) and 1,3-di-epi-pochonicine
4L) in excellent yields (94% and 98%, respectively). The
(
intermediates 24L, 25L, 26L, and 27L were relatively unstable
at room temperature, especially compound 26, which needed to
be handled carefully and was best used directly in the next
reaction step immediately after purification.
The structures of (−)-pochonicine 1L, 3-epi-pochonicine 2L,
-epi-pochonicine 3L, and 1,3-di-epi-pochonicine 4L were
1
characterized spectroscopically, including detailed 600 MHz
NOESY experiments (Figure 4). The NOESY spectrum of 1L
yield, respectively. Deprotection of the two N-Boc groups of
25
mesylate 20L by treatment with ZnBr in CH Cl followed by
2
2
2
cyclization under basic conditions (K CO /MeOH) yielded
2
3
protected pyrrolidine 24L in moderate yield (42% over two
steps). After global deprotection of 24L, the target compound
(
−)-pochonicine (1L) was obtained in 98% yield. By a similar
procedure, 3-epi-pochonicine (2L) was synthesized from 21L
(
Scheme 3).
Figure 4. Main NOE interactions for natural pochonicine, 1L, 2L, 3L,
and 4L.
The other two epimers of (−)-pochonicine 1L, compounds
L and 4L, were synthesized staring from 17L through the
3
same procedure as for the synthesis of 1L and 2L (Scheme 4).
Thus, dihydroxylation of 17L and selective TBDMS protection
of the primary hydroxyl group afforded 19aL and 19bL in 86%
total yield over two steps. Mesylation of 19aL and 19bL gave
mesylates 22L and 23L in 92% and 93% yield, respectively.
Deprotection of the two N-Boc groups of mesylates 22L and
showed strong NOE interactions between H-1 and H-8, H-5
and H-8, H-7 and H-9, and H-6 and H-7a. The characterization
of compound 2L was confirmed by NOE interactions between
H-1 and H-3 and H-3 and H-5. Interestingly, an NOE
interaction between H-1 and H-7 could be observed in 1L and
2L, which was contradictory to the trans configuration between
H-1 and H-7 proved by the X-ray crystal structure of
compound 15bL. This unusual NOE interaction in 1L and
Scheme 4. Synthesis of (−)-1-epi-Pochonicine (3L) and
(
−)-1,3-Di-epi-pochonicine (4L)
2L might be ascribed to the folding arrangement of the two
pyrrolidine rings to give a twisted conformation of the bicyclic
skeleton, making H-1 close to H-7. Similarly, the character-
ization of 3L was also confirmed by interactions between H-1
and H-3 and H-5 and H-8; the characterization of 4L was
confirmed by the NOE interaction between H-1 and H-8.
In order to determine the absolute configuration of the
natural product pochonicine and to perform a preliminary
investigation of the structure−activity relationships of pocho-
nicine and its analogues, the corresponding enantiomers of 1L,
2
L, 3L, and 4L, namely, (+)-pochonicine (1D), 3-epi-
pochonicine (2D), 1-epi-pochonicine (3D), and 1,3-di-epi-
pochonicine (4D), were synthesized through the same
synthetic route from the L-ribose-derived cyclic nitrone 9D.
Unequivocal Structure Determination of Natural
Pochonicine. The determination of the relative configuration
1
of natural pochonicine was made by comparison of the H and
13
C NMR spectra of the synthetic compounds 1L−4L with
those of the natural product. As has been reported by
8
1
13
Takahashi and co-workers, the H and C NMR spectra of
compound 4L, the structure of pochonicine proposed by
Nitoda, are not consistent with those of the isolated natural
1
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Figure 5. Comparison of the NMR spectra (300 MHz, D O) of 1D and 1L with those of the natural sample: (A) natural sample supplied by the
2
Nitoda group; (B) synthetic (+)-pochonicine 1D; (C) synthetic (−)-pochonicine 1L.
Table 1. Concentrations of Synthetic (+)-Pochonicine and Its Isomers Giving 50% Inhibition of Various Glycosidases
IC50 (μM)
(
+)-pochonicine
(+)-3-epi-pochonicine
(+)-1-epi-pochonicine
(+)-1,3-di-epi-pochonicine
naturalc
sample
enzyme
1D
2D
3D
4D
a
b
α-L-rhamnosidase from P. decumbens
β-N-acetylglucosaminidases
A. oryzae
NI (0.3%)
694
NI (5.1%)
674
NI (0.3%)
0.33
NI (44.4%)
1.2
11
11
0.31
bovine kidney
0.021
0.51
0.49
0.019
HL-60
0.018
0.61
0.38
0.46
0.014
human placenta
jack bean
0.012
0.38
0.22
0.30
0.011
0.0016
NI (9.0%)
0.24
0.042
NI (4.6%)
0.046
NI (7.5%)
0.0013
NI (12.9%)
α-N-acetylgalactosaminidase from chicken
NI (11.8%)
liver
β-N-acetylgalactosaminidases
A. oryzae
0.30
NI (47.4%)
9.1
12
0.24
HL-60
0.049
2.0
1.4
1.9
0.038
a
b
c
NI: No inhibition (less than 50% inhibition at 1000 μM). (): inhibition % at 1000 μM. Natural sample: our tested results for the natural
pochonicine supplied by the Nitoda group.
1
pochonicine. Among the four synthetic isomers of pochonicine,
by comparison of the H and 13C NMR spectra of 1D with
those of natural pochonicine, which showed that the two
matched perfectly with each other (Figure 5)
1
13
compounds 1L, 2L, 3L, and 4L, the H and C NMR spectra
of 1L were the most similar to those of the natural pochonicine.
This suggested that the natural product pochonicine may
possess the same relative configuration as 1L. However, the
As mentioned in the Introduction of this article, the absolute
configuration of natural pochonicine was determined to be that
of compound 1D (the enantiomer of 1L) by Takahashi and co-
workers. Although the optical rotation of compound 1D {[α]
+3.0 (c 1.74, MeOH)} had the same sign as that of the natural
sample of pochonicine{[α] +9.2 (c 0.89, MeOH)}, the very
small values of the optical rotations of the free bases made the
determination of the absolute configuration on the basis of such
a comparison of optical rotation unreliable; the determination
of the absolute configuration through the optical rotations of
the hydrogen chloride salts of compound 1L and the natural
1
13
reported H and C NMR spectra of compound 1L were quite
different from those of the natural sample of pochonicine,
although they looked similar at first glance. After an in-depth
study of the NMR spectra of the natural product pochonicine
and the synthetic samples, it was found that when measured in
8
D
8
1
D
1
13
D O, the H and C NMR spectra of 1L matched very well
2
with those of the natural pochonicine (Figure 5), which
unambiguously confirmed the relative configuration of the
natural pochonicine as that of 1L. This was further confirmed
1
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Table 2. Concentrations of Synthetic (−)-Pochonicine and Its Isomers Giving 50% Inhibition of Various Glycosidases
IC50 (μM)
(
−)-pochonicine
(−)-3-epi-pochonicine
(−)-l-epi-pochonicine (−)-1,3-di-epi-pochonicine
3L 4L
Nitoda’s
d
enzyme
1L
2L
results
c
α-L-rhamnosidase from P. decumbens
β-N -acetylglucosaminidases
A. oryzae
291
1.2
323
82
ND
a
b
NI (39.6%)
NI (0%)
NI (0%)
NI (0%)
0.0203
0.00106
ND
bovine kidney
90
NI (27.6%)
NI (38.1%)
NI (36.5%)
501
NI (33.7%)
NI (32.2%)
NI (29.9%)
191
NI (29.4%)
NI (18.3%)
NI (19.9%)
NI (32.7%)
NI (44.4%)
HL-60
85
human placenta
jack bean
62
0.00239
0.000288
ND
31
α-N -acetylgalactosaminidase from chicken
liver
NI (14.6%)
NI (36.8%)
NI (31.8%)
β-N-acetylgalactosaminidases
A. oryzae
NI (40.2%)
274
NI (0%)
NI (0%)
NI (0%)
ND
ND
HL-60
NI (10.5%)
NI (11.8%)
NI (7.4%)
a
b
c
d
NI: no inhibition (less than 50% inhibition at 1000 μM). (): % inhibition at 1000 μM. ND: not detected. Nitoda’s result: Nitoda and co-
1
workers originally reported these results in 2009.
sample of pochonicine was also not to be trusted. With both
enantiomers of pochonicine (1D and 1L) in hand, the
determination of the absolute configuration of the natural
product pochinicine became more reliable. The optical
inhibition against these enzymes. However, 3-epi-pochonicine
2L is a potent and selective inhibitor of Penicillium decumbens α-
L-rhamnosidase, with IC = 1.2 μM. This inhibition potency is
50
similar to that of the known potent α-L-rhamnosidase inhibitor
35
26
rotations of 1L, 1D, and natural pochonicine {[α] −1.07 (c
L-swainsonine but weaker than that of (6R)-C-methyl-L-
D
2
0
20
27
0
0
.90, MeOH), [α] +0.74 (c 0.70, MeOH), and [α]D +9.2 (c
.89, MeOH), respectively} confirmed the absolute config-
swainsonine. These glycosidase inhibition data strongly
D
1
support the assignment of the absolute configuration of natural
pochonicine as (+)-(1R,3S,5R,6R,7S,7aR)-pochonicine (1D).
uration of the natural pochonicine as (1R,3S,5R,6R,7S,7aR)-1D,
in agreement with the results reported by Takahashi and co-
workers. This was to be further proved by the comparison of
the glycosidase inhibition profiles of 1L and 1D with that of the
natural product.
Glycosidase Inhibition. To compare the glycosidase
inhibition activities of the synthetic compounds with those of
the natural pochonicine, all the synthetic compounds 1D−4D
and 1L−4L were assayed together with natural pochonicine as
potential glycosidase inhibitors against a range of enzymes
CONCLUSIONS
■
(
+)-Pochonicine (1D) and its C-1 and/or C-3 epimers 2D, 3D,
and 4D as well as the corresponding enantiomers 1L, 2L, 3L,
and 4L have been synthesized from sugar-derived nitrones 9D
and 9L, respectively. The key features of this synthetic strategy
include (1) the use of the initial nitrone to provide the
trihydroxylated pyrrolidine ring with the desired stereo-
chemistry, (2) the installation of the required acetamidomethyl
group at an early stage of the synthesis via acetylation of the
primary amide by the reduction of a CN group and acylation,
and (3) construction of the second pyrrolidine ring through an
(
Tables 1 and 2). It was found that natural pochonicine is
indeed a powerful inhibitor (with IC50 at the nanomolar level)
against jack bean, human placenta, HL-60, bovine kidney, and
Aspergillus oryzae β-GlcNAcases (IC = 1.3, 11, 14, 19, and 310
5
0
intramolecular S 2 displacement. The relative configuration of
N
nM, respectively). Furthermore, it also exhibited potent
inhibition against HL-60 and A. oryzae β-N-acetylgalactosamin-
idases (β-GalNAcases), with IC50 = 38 and 240 nM,
respectively. The synthetic (+)-pochonicine 1D showed potent
inhibition against jack bean, human placenta, HL-60, bovine
the natural product pochonicine has been unequivocally
determined through an in-depth NMR study, which showed
1
13
that both the H and C NMR spectra of the synthetic
pochonicines (1D and 1L) matched with those of the natural
pochonicine in D O, thereby confirming the relative config-
2
kidney, and A. oryzae β-GlcNAcases (IC = 1.6, 12, 18, 21, and
5
0
uration of the natural product as that of 1D or 1L. In addition
to a comparison of the optical rotations of the synthetic
pochonicines with that of the natural product, a comparison of
the glycosidase inhibition profiles of both enantiomers of each
pochonicine with that of the natural product further confirmed
the absolute configuration of the natural pochonicine as
330 nM, respectively) and HL-60 and A. oryzae β-GalNAcases
(
IC50 = 49 and 300 nM, respectively). These nanomolar
inhibition potencies were almost exactly the same. It is
noteworthy that all three of the epimers 2D, 3D, and 4D are
about 10-fold weaker inhibitors than (+)-pochonicine 1D and
the natural product but are still potent. It is also noteworthy
that none of the compounds mentioned above showed any
inhibition of α-GalNAcase.
In contrast, the enantiomers (−)-pochonicine 1L, (−)-3-epi-
pochonicine 2L, (−)-1-epi-pochonicine 3L, and (−)-1,3-di-epi-
pochonicine 4L were found to be much weaker inhibitors
1
R,3S,5R,6R,7S,7aR. Thus, the structure of the natural
pochonicine has unequivocally bee determined as
(+)-(1R,3S,5R,6R,7S,7aR)-pochonicine (1D) in agreement
with the data reported by Takahashi and co-workers.
Glycosidase inhibition experiments showed that natural
pochonicine 1D and its epimers 2D, 3D, and 4D all are
powerful inhibitors of hexosaminidases (five β-GlcNAcases and
two β-GalNAcases), but their enantiomers 1L, 2L, 3L, and 4L
are much weaker inhibitors of the same enzymes. (−)-3-epi-
Pochonicine (2L) was found to be a potent and selective
inhibitor of α-L-rhamnosidase. None of the compounds showed
(
Table 2). Compound 1L displayed only moderate inhibition
of jack bean, human placenta, HL-60, and bovine kidney
GlcNAcases (IC50 = 31, 62, 85, and 90 μM, respectively) and
HL-60 β-GalNAcase (IC = 274 μM). Furthermore, the other
5
0
three isomers 2L, 3L, and 4L did not show any significant
1
0303
dx.doi.org/10.1021/jo401694e | J. Org. Chem. 2013, 78, 10298−10309

The Journal of Organic Chemistry
Article
any inhibition of α-GalNAcase. The results obtained from the
preliminary structure−activity relationship study are valuable
for future work on the design and synthesis of pochonicine-
based inhibitors of β-N-acetylhexosaminidases.
2,3-O-Isopropylidene-4-O-methanesulfonyl-5-O-trityl-D-ri-
bose-O-(tert-butyldimethylsilyl) Oxime (8L). The syrup 7L (406
g) was dissolved in dry CH Cl (500 mL), and triethylamine (112.0
2
2
mL, 0.81 mol) was added. Then methanesulfonyl chloride (52.0 mL,
0
.64 mol) was added dropwise to the above solution at 0 °C. When
the addition was complete, the mixture was stirred for 1 h at the same
EXPERIMENTAL SECTION
temperature. H O (200 mL) was added to quench the reaction. The
2
■
mixture was extracted. The organic layer was washed with H O (3 ×
2
General Methods. All reagents were used as received from
commercial sources or prepared as described in the literature. TLC
plates were visualized by ultraviolet light or by treatment with a spray
of Pancaldi reagent or a solution 0.5% ninhydrin in acetone. Acidic ion
5
0 mL), dried (MgSO ), and concentrated under vacuum to give 500
4
g of light-yellow syrup. A 200 mg sample of the syrup was purified by
column chromatography on silica gel (petroleum ether/EtOAc 30:1)
to give an inseparable E/Z mixture of 8L.
+
exchange chromatography was performed on Amberlite IR-120 (H )
1
+
Data for 8L (E/Z mixture, E/Z = 1.6 as determined by H NMR):
or Dowex 50WX8-400, H form. Melting points were determined
1
5
−1
[
(
α] +26 (c 1.0, CH Cl ). IR (neat, cm ): 3080, 3033, 2929, 1598
D 2 2
using an electrothermal melting point apparatus. NMR spectra were
measured in CDCl (with TMS as an internal standard) or D O on a
1
CN), 1492, 1449, 1362, 1178, 930. H NMR (CDCl , 300 MHz):
3
3
2
1
13
δ 7.46−7.40 (m, 11H), 7.33−7.22 (m, 22H), 6.68 (d, J = 3.6 Hz, 1H),
magnetic resonance spectrometer ( H at 300 or 600 MHz, C at 75 or
50 MHz). Chemical shifts (δ) are reported in parts per million, and
5
2
8
6
.18 (dd, J = 8.1 and 3.9 Hz, 1H), 4.95−4.90 (m, 2H), 4.80−4.72 (m,
H), 4.55−4.51 (m, 1H), 3.42−3.40 (m, 2H), 3.25 (dd, J = 11.7 and
.4 Hz, 1H), 3.07 (s, 2H), 2.99 (s, 3H), 1.54 (s, 3H), 1.34−1.32 (m,
H), 1.28−1.25 (m, 2H), 1.0 (s, 6H), 0.92 (s, 9H), 0.29 (s, 4H), 0.16
1
coupling constants (J) are in hertz. The following abbreviations are
used to explain the multiplicities: s = singlet, d = doublet, t = triplet, q
quartet, m = multiplet. High-resolution mass spectrometry (HRMS)
was performed on an LTQ/FT linear ion trap mass spectrometer.
Optical rotation measurements were made with an Autopol VI
instrument at the sodium D-line using a cell with a path length of 0.25
dm. Concentrations (c) are given in grams per 100 mL.
,3-O-Isopropylidene-5-O-trityl-D-ribose-O-(tert-butyl-
dimethylsilyl) Oxime (7L). According to the reported procedure,
=
(
s, 6H). 13C NMR (CDCl , 75 MHz): δ 152.4, 151.2, 143.4, 128.8,
3
1
7
2
28.7, 128.1, 127.4, 109.8, 109.4, 87.43, 87.37, 81.7, 79.2, 78.7, 77.5,
6.7, 74.7, 72.1, 64.7, 62.0, 39.1, 39.0, 29.8, 27.1, 26.3, 26.1, 25.8, 25.0+,
3.9, 18.3, 18.2, −5.1, −5.13, −5.2. HRMS (ESI) m/z: [M + Na]
+
calcd for C H NO SSiNa 662.2578; found 662.2575.
2
34 45
7
1
4
1
Data for 8D (E/Z mixture, E/Z = 1.8 as determined by H NMR):
1
5
+
[
α] −36 (c 1.0, CH Cl ). HRMS (ESI) m/z: [M + Na] calcd for
oxime 6L was obtained in three steps from D-ribose (6D from L-ribose
is an unknown compound). To an ice-cold solution of oxime 6L
D
2
2
+
C H NO SSiNa 662.2578; found 662.2573.
34 45
7
1
-Amino-1,4-anhydro-1,N-didehydro-2,3-O-isopropylidene-
(
(
300.0 g, 0.53 mol) in CH Cl (700 mL) was added triethylamine
2 2
5
-O-trityl-D-ribitol N-Oxide (9L). Tetrabutylammonium fluoride
112.0 mL, 0.81 mol) followed by dropwise addition of a solution of
tert-butylchlorodimethylsilane (96.0 g, 0.64 mol) in CH Cl (150.0
mL). After the addition, the mixture was stirred at the same
temperature overnight. The reaction was quenched carefully with
H O (200 mL). The mixture was transferred to a funnel. The organic
(
(
152.16 g, 0.58 mol) was added to a solution of 8L (500 g) in toluene
500 mL) at 0 °C. The mixture was stirred for 30 min, transferred to
2
2
an oil bath and heated at reflux overnight, and then cooled to room
temperature. The solvent was removed under vacuum to give a black
residue, which was extracted with EtOAc (3 × 50 mL), dried
2
layer was washed with H O (3 × 50 mL), dried (MgSO ), and
2
4
(
MgSO ), concentrated under vacuum, and purified by column
concentrated under vacuum to give 406 g of colorless syrup. About
4
chromatography on silica gel (petroleum ether/EtOAc 3:1 then 2:1)
to afford 9L (50 g) as a yellow foam. The overall yield from D-ribose to
nitrone 9L was 22%.
2
00 mg of the syrup was purified by column chromatography on silica
gel (petroleum ether/EtOAc 20:1) to give an inseparable E/Z mixture
of 7L.
1
5
1
Data for 9L: Mp 88−90 °C. [α] +20 (c 1.0, CH Cl ). IR (neat,
Data for 6D (E/Z mixture, E/Z = 3.2 as determined by H NMR):
D
2
2
2
D
5
−1
−1
1
[
3
(
(
1
3
(
1
1
8
α] −8 (c 1.0, CH Cl ). IR (neat, cm ): 3556 (OH), 3087, 3059,
cm ): 3058, 2936, 1574 (CN), 1491, 1448, 1211, 1075, 706. H
2
2
1
033, 2987, 2935, 1597(CN), 1491, 1448, 1220, 1065. H NMR
NMR (CDCl , 300 MHz): δ 7.50−7.44 (m, 7H), 7.28−7.16 (m, 8H),
3
300 MHz,CDCl ): δ 7.48−7.42 (m, 8H), 7.33−7.23 (m, 11H), 6.83
6.76 (m, 1H), 5.09−5.07 (m, 1H), 4.89−4.85 (m, 1H), 4.11−4.09 (m,
1H), 3.92 (dd, J = 9.0 and 4.2 Hz, 1H), 3.68−3.62 (m, 1H), 1.32 (s,
3
d, J = 6.0 Hz, 0.23H), 5.34 (t, J = 6.0 Hz, 0.25H), 4.77 (t, J = 6.0 Hz,
3H), 1.22 (s, 3H). 13C NMR (CDCl
, 75 MHz): δ 143.5, 132.8, 128.6,
H), 4.42−4.37 (m, 0.24H), 4.22 (dd, J = 9.0 and 6.0 Hz, 1H), 3.79−
3
.74 (m, 1H), 3.42−3.23 (m, 2H), 2.81−2.79 (m, 0.2H), 2.60−2.58
127.6, 126.9, 111.7, 87.1, 77.6, 74.8, 73.9, 58.6, 26.9, 25.9. HRMS
+
+
m, 1H), 1.65−1.56 (m, 1H), 1.52−1.50 (m, 0.33H), 1.40 (m, 2H),
(ESI) m/z: [M + Na] calcd for C27
H
27NO
4
Na 452.1832; found
13
.35−1.31 (m, 4H). C NMR (75 MHz, CDCl ): δ 150.4, 148.5,
452.1833.
3
1
5
44.1, 143.9, 128.9, 128.8, 128.0, 127.9, 127.3, 127.1, 110.0, 109.6,
7.1, 86.9, 78.3, 75.4, 71.3, 70.3, 69.0, 65.3, 27.9, 27.4, 25.6, 25.3.
Data for 9D: 25% yield from L-ribose, mp 85−87 °C. [α] −20 (c
D
+
+
1.0, CH
Cl ). HRMS (ESI) m/z: [M + Na] calcd for C27H27NO Na
2 4
2
+
+
HRMS (ESI) m/z: [M + Na] calcd for C H NO Na 470.1938;
452.1832; found 452.1830.
27
29
5
found 470.1937.
Data for 7L (E/Z mixture, E/Z = 2.9 as determined by H NMR):
(2S,3S,4R,5S)-2,3-O-Isopropylidene-5-(trityloxymethyl)-1-
hydroxypyrrolidine-2-carbonitrile (10L). To a solution of nitrone
9L (40.00 g, 0.09 mol) in dry methanol (100.0 mL) was added
trimethylsilyl cyanide (13.0 mL, 0.095 mol), and the resulting solution
was stirred at 50 °C under an argon atmosphere overnight. The
reaction solvent was removed under vacuum to give a light-yellow
spumescent solid that could be crystallized from methanol to yield a
white solid (30.00 g, 73%). The mother liquid was purified by column
chromatography on silica gel (petroleum ether/EtOAc 6:1) to afford
1
15
−1
[
2
α] +20 (c 1.0, CH Cl ). IR (neat, cm ): 3483 (OH), 3059, 2930,
D 2 2
1
857, 1598 (CN), 1491, 1449, 1252, 1220, 1066, 934, 839, 706. H
NMR (CDCl , 300 MHz): δ 7.35 (d, J = 7.5 Hz, 1H), 7.30−7.27 (m,
8
0
(
3
H), 7.16−7.05 (m, 17H), 6.76 (d, J = 5.4 Hz, 0.34H), 5.17−5.13 (m,
.34H), 4.62 (dd, J = 7.5 and 6.3 Hz, 1H), 4.28−4.23 (m, 0.34H), 4.08
dd, J = 9.0 and 6.3 Hz, 1H), 3.62−3.56 (m, 1H), 3.24−3.15 (m, 2H),
3
0
8
.13−3.05 (m, 1H), 2.56 (d, J = 3.6 Hz, 0.27H), 2.35 (d, J = 6.1 Hz,
.27H), 1.41−1.38 (m, 2H), 1.37−1.35 (m, 0.43H), 1.22−1.16 (m,
hydroxylamine 10L (9.30 g), total yield 96%.
13
15
H), 0.80 (s, 3H), 0.77 (s, 9H), 0.05−0.04 (m, 2H), 0 (s, 6H).
C
Data for 10L: Mp 162−165 °C. [α]
D
+60 (c 1.0, CH
Cl
2
). IR (neat,
2
−
1
NMR (CDCl , 75 MHz): δ 154.1, 152.4, 144.0, 143.8, 128.8, 128.7,
cm ): 3420 (br, OH), 3058, 2939, 1491 (m), 1448 (m), 1380 (m),
3
1
1
6
27.9, 127.2, 127.0, 109.8, 109.3, 86.9, 86.7, 78.6, 77.9, 75.4, 71.8, 70.4,
1214 (s), 1076 (s), 705 (s). H NMR (CDCl , 300 MHz): δ 7.46−
3
9.1, 65.3, 65.0, 27.8, 27.3, 26.1, 26.07, 25.5, 25.1, 18.2, 18.1, −5.2,
7.43 (m, 6H), 7.28−7.17 (m, 9H), 5.69 (s, 1H), 4.79 (dd, J = 6.6 and
5.1 Hz, 1H), 4.72−4.70 (m, 1H), 4.25−4.23 (m, 1H), 3.56−3.51 (m,
+
−
5.24. HRMS (ESI) m/z: [M + Na]+ calcd for C H NO SiNa
33 43 5
5
84.2803; found 584.2799.
Data for 7D (E/Z mixture, E/Z = 2.3 as determined by H NMR):
1H), 3.36 (dd, J = 8.7 and 5.4 Hz, 1H), 3.18−3.12 (m, 1H), 1.26−1.23
1
13
(m, 6H). C NMR (CDCl , 75 MHz): δ 143.7, 128.8, 127.9, 127.2,
3
2
5
+
[
α] = +2 (c 1.0, CH Cl ). HRMS (ESI) m/z: [M + H] calcd for
114.8, 112.4, 87.3, 78.7, 76.9, 67.9, 62.4, 60.9, 25.6, 24.9. HRMS (ESI)
D
2
2
+
+
+
C H NO Si 562.2983; found 562.2982.
m/z: [M + Na] calcd for C H N O Na 479.1941; found 479.1946.
33
44
5
28 28
2 4
1
0304
dx.doi.org/10.1021/jo401694e | J. Org. Chem. 2013, 78, 10298−10309

The Journal of Organic Chemistry
Article
2
2
Data for 10D: 88% yield, mp 164−167 °C. [α] −56 (c 1.0,
vacuum. The residue was purified by column chromatography on silica
gel (petroleum ether/EtOAc 4:1) to give alcohol 13L (5.63 g, 58%).
D
+
+
CH Cl ). HRMS (ESI) m/z: [M + Na] calcd for C H N O Na
2
2
28 28
2
4
Data for 13L: [α]2
5
−18 (c 1.0, CH Cl ). IR (neat, cm ): 3432 (br,
−1
4
79.1941; found 479.1937.
(
D
2 2
2S,3S,4R,5S)-1-N-tert-Butoxycarbonyl-2-(tert-butoxy-
carbonylamidomethyl)-3,4-O-isopropylidene-5-(trityloxy-
methyl)pyrrolidine (11L). To a solution of hydroxylamine 10L
OH), 2980 (m), 1737 (s, CO), 1679 (s, CO), 1370 (m), 1148
1
(m). H NMR (CDCl , 300 MHz): δ 5.12 (dd, J = 9.0 and 4.8 Hz,
3
1H), 4.67−4.64 (m, 1H), 4.41−4.31 (m, 2H), 3.87−3.85 (m, 2H),
1
3
(
20.00 g, 0.044 mol) in THF/MeOH (10:1) was added di-tert-butyl
3.79−3.60 (m, 3H), 2.44 (s, 3H), 1.51−1.24 (m, 24H). C NMR
dicarbonate (24.00 g, 0.11 mol) followed by Raney nickel (10.00 g).
After being stirred under a hydrogen atmosphere at room temperature
for 4 days, the reaction mixture was filtered through Celite, and the
filtrate was concentrated and extracted with EtOAc (3 × 100 mL) and
water (50.0 mL). The combined organic extracts were dried (MgSO4)
and then concentrated to give a white foam, which was purified by
column chromatography on silica gel (petroleum ether/EtOAc 8:1) to
give 11L (26.10 g, 92%) as a white foam.
(CDCl , 75 MHz): δ 172.8, 155.7, 152.9, 111.5, 84.4, 81.1, 80.5, 79.9,
3
64.1, 62.4, 61.3, 43.1, 28.4, 28.1, 27.3, 26.3, 24.9. HRMS (ESI) m/z:
+
+
[M + H] calcd for C H N O 445.2544; found 445.2542.
21
37
2
8
2
4
D
Data for 13D: 57% yield, [α] +16 (c 1.0, CH Cl ). HRMS (ESI)
m/z: [M + H] calcd for C H N O 445.2544; found 445.2542.
2
2
+
+
21
37
2
8
(2S,3S,4R,5S)-1-N-tert-Butoxycarbonyl-2-(N-tert-butoxy-
carbonylacetylamidomethyl)-3,4-O-isopropylidene-5-(((1S)-1-
hydroxy-3-butenyl))pyrrolidine (15aL) and (2S,3S,4R,5S)-1-N-
tert-Butoxycarbonyl-2-(N-tert-butoxycarbonylacetylamido-
methyl)-3,4-O-isopropylidene-5-(((1R)-1-hydroxy-3-butenyl))-
pyrrolidine (15bL). To Dess−Martin periodinane (5.00 g, 11.8
mmol) suspended in dry CH Cl (20.0 mL) was added NaHCO
1
5
Data for 11L: Mp 76−78 °C. [α] +40 (c 1.0, CH Cl ). IR (neat,
D
2
2
−1
cm ): 3360 (NH), 2978 (m), 1764 (m), 1710 (s, CO), 1495 (m),
1
(
4
4
1
449 (m), 1359 (m), 1249 (m), 1164 (m), 704 (m). 1H NMR
2
2
3
CDCl , 300 MHz): δ 7.42−7.39 (m, 5H), 7.26−7.10 (m, 10H),
3
(1.22 g, 14.8 mmol) followed by alcohol 13L (2.62 g, 5.9 mmol)
.84−4.82 (m, 1H), 4.73−4.70 (m, 1H), 4.58−4.56 (m, 1H), 4.48−
.39 (m, 1H), 3.81−3.79 (m, 1H), 3.73−3.70 (m, 1H), 3.50−3.48 (m,
dissolved in dry CH Cl2 (20.0 mL). After being stirred at room
2
temperature for 1 h, the reaction mixture was diluted with diethyl
ether (30 mL). The reaction was quenched with saturated sodium
thiosulfate solution (20 mL), and the mixture was stirred vigorously
until two clear layers appeared. It was then extracted with ethyl ether
13
H), 3.39−3.14 (m, 3H), 1.36−1.19 (m, 23H). C NMR (CDCl , 75
3
MHz): δ 156.2, 153.1, 144.3, 144.1, 128.9, 128.88, 128.7, 128.5, 127.9,
1
8
[
27.7, 127.6, 127.5, 127.2, 126.9, 126.87, 112.9, 112.5, 86.9, 86.8, 83.2,
0.4, 80.05, 79.5, 68.1, 65.2, 64.5, 61.2, 60.5, 40.5. HRMS (ESI) m/z:
M + Na] calcd for C H N O Na 667.3354; found 667.3342.
(3 × 50 mL). The combined organic extracts were washed with water
+
+
38 48 2 7
and brine, dried over magnesium sulfate, and concentrated in vacuo to
give aldehyde 14L as a light-yellow residue that was directly used in
the next step without further purification. To a solution of aldehyde
1
5
Data for 11D: 89% yield, mp 76−77 °C. [α] −46 (c 1.0, CH Cl ).
D
2
2
+
+
HRMS (ESI) m/z: [M + Na] calcd for C H N O Na 667.3354;
38
48
2
7
found 667.3347.
2S,3S,4R,5S)-1-N-tert-Butoxycarbonyl-2-(N-tert-butoxy-
carbonylacetylamidomethyl)-3,4-O-isopropylidene-5-(trityl-
oxymethyl)pyrrolidine (12L). Commercially available lithium
diisopropylamide (13.0 mL, 0.27 mol, 2 M in hexane) was added
dropwise at −78 °C under an argon atmosphere to a solution of 11L
12.00 g, 0.019 mol) in freshly distilled THF (110 mL). After the
addition, the mixture was stirred for 20 min, and then acetic anhydride
6.3 mL, 0.057 mol) was added dropwise. The mixture and stirred
vigorously for 20 min. Caution: the mixture turned extremely sticky
at −78 °C when Ac O was added, so it is important to stir
vigorously for better conversion. The mixture was allowed to warm
to room temperature, and the reaction was quenched with saturated
aq. NH Cl. The mixture was extracted with EtOAc (3 × 50 mL), dried
MgSO ), concentrated under vacuum, and purified by column
chromatography on silica gel (petroleum ether/EtOAc 8:1) to afford
1
4L in THF (5 mL) were added allylic bromide (4.1 mL, 29.5 mmol)
(
and zinc dust (3.11 g, 59 mmol) followed by the dropwise addition of
saturated NH Cl solution. After 5 min, more allylic bromide (16.4 mL,
4
1
18 mmol) and zinc dust (12.4 g, 236 mmol) were carefully added in
four portions. Then the reaction was allowed to stir at room
temperature for 4 h. The reaction mixture was filtered through Celite,
and the filtrate was extracted with EtOAc (3 × 100 mL). The
combined organic layers were washed with water and brine, dried
(
(
(
MgSO ), and then concentrated. The residue was purified by column
4
chromatography on silica gel (petroleum ether/EtOAc 5:1) to afford a
mixture of alcohol 15aL (1.49 g) as a white solid and 15bL (1.09 g) as
a colorless oil, total yield 89%.
2
31
−1
Data for 15aL: [α]D +7 (c 1.15, CH Cl ). IR (neat, cm ): 3440
2
2
4
(OH), 2979 (m), 2935 (m), 1737 (s, CO), 1682 (s, CO), 1369
(
1
4
(s), 1147 (s). H NMR (CDCl , 300 MHz): δ 5.92−5.81 (m, 1H),
3
5
4
2
.04−4.94 (m, 2H), 4.72−4.68 (m, 1H), 4.52−4.51 (m, 1H), 4.37−
.17 (m, 3H), 3.87 (dd, J = 13.8 and 7.5 Hz, 1H), 3.72−3.58 (m, 1H),
.60−2.55 (m, 2H), 2.39 (m, 4H), 2.27−2.18 (m, 1H), 1.48−1.20 (m,
1
1
2L (10.40 g, 79.8%) as a white foam and recovered starting material
1L (1.62 g).
1
5
Data for 12L: Mp 66−68 °C. [α] +18 (c 1.0, CH Cl ). IR (neat,
13
D
2
2
24H). C NMR (CDCl , 75 MHz): δ 172.9, 155.7, 152.7, 136.3,
3
−1
cm ): 2979 (m), 1737 (s, CO), 1608 (s, CO), 1449 (m), 1369
1
15.9, 111.4, 84.0, 80.8, 79.4, 69.6, 65.3, 61.7, 43.1, 38.4, 28.2, 28.0,
1
(
m), 1218 (m), 1150 (m), 1069 (m), 704 (s). H NMR (CDCl , 300
+
+
3
27.0, 25.7, 24.1. HRMS (ESI) m/z: [M + H] calcd for C H N O
24 41 2 8
MHz): δ 7.50−7.48 (m, 6H), 7.30−7.19 (m, 9H), 4.98−4.96 (m, 1H),
4
85.2857; found 485.2853.
Data for 15aD: [α]1 −8 (c 1.0, CH Cl ). 70% combined yield over
4
4
3
7
1
6
.41−4.39 (m, 1H), 3.93−3.90 (m, 1H), 3.75−3.73 (m, 3H), 3.61−
D
2
2
13
+
.59 (m, 1H), 2.44 (s, 3H), 1.44−1.22 (m, 24H). C NMR (CDCl ,
3
two steps, 15aD:15bD = 1.7:1. HRMS (ESI) m/z: [M + H] calcd for
C H N O 485.2857; found 485.2855. 3
+
5 MHz): δ 173.4, 172.8, 152.7, 152.65, 152.59, 144.2, 144.0, 128.8,
27.6, 127.5, 126.7, 112.2, 111.0, 86.7, 86.6, 83.3, 82.3, 80.8, 79.5, 67.1,
2.5, 59.9, 42.4, 28.1, 27.9, 27.6, 26.9, 26.5, 26.0, 25.4. HRMS (ESI)
24
41
2
8
1
D
Data for 15bL: Mp 107−108 °C. [α] −38 (c 1.0, CH Cl ). IR
2
2
−1
(neat, cm ): 3383 (s, OH), 2979 (m), 2938 (m), 1737 (s, CO),
+
+
1
m/z: [M + Na] calcd for C H N O Na 709.3459; found 709.3468.
Data for 12D: 72% (77% brsm) yield, mp 65−68 °C. [α] −20 (c
.0, CH Cl ). HRMS (ESI) m/z: [M + Na] calcd for
1676 (s, CO), 1422 (m), 1370 (m), 1225 (m). H NMR (CDCl ,
40
50
2
8
3
1
5
D
300 MHz): δ 6.02−5.97 (m, 1H), 5.91 (s, 1H), 5.11−5.00 (m, 2H),
4.52 (dd, J = 6.0 and 3.6 Hz, 1H), 4.44 (dd, J = 9.6 and 6.0 Hz, 1H),
4.24−4.20 (m, 2H), 3.71−3.57 (m, 2H), 3.39 (dd, J = 8.7 and 3.3 Hz,
1H), 2.60−2.55 (m, 1H), 2.41 (s, 3H), 2.36−2.29 (m, 1H), 1.47−1.20
+
1
2
2
+
C H N O Na 709.3459; found 709.3453.
4
0
50
2
8
(
2S,3S,4R,5S)-1-N-tert-Butoxycarbonyl-2-(N-tert-butoxy-
(m, 24H). 13C NMR (CDCl , 75 MHz): δ 172.8, 155.5, 152.8, 135.4,
carbonylacetylamidomethyl)-3,4-O-isopropylidene-5-
3
(
(
hydroxymethyl)pyrrolidine (13L). To an ice-cold solution of 12L
1
2
16.7, 111.4, 84.2, 81.0, 80.2, 79.7, 67.7, 67.3, 63.5, 42.8, 38.0, 28.3,
15.00 g, 0.022 mol) in dry ethyl ether (200.0 mL) was added
+
8.0, 27.2, 26.6, 25.0. HRMS (ESI) m/z: [M + H] calcd for
+
HCOOH (200.0 mL). The mixture was stirred at the same
temperature for 1 h and then warmed to room temperature with
stirring for another 30 min. Then the reaction mixture was diluted with
EtOAc (200 mL), and the reaction was carefully quenched with solid
NaHCO until there was no effervescence. The organic layer was
washed with water and brine, dried (MgSO ), and concentrated under
C H N O 485.2857; found 485.2849.
24
41
2
8
2
8
Data for 15bD: Mp 105−106 °C. [α] +40 (c 1.0, CH Cl ). HRMS
D
2
2
+
+
(ESI) m/z: [M + H] calcd for C H N O 485.2857; found
24 41 2 8
485.2855.
3
General Procedure for the Synthesis of 16L and 17L.
(2S,3S,4R,5S)-1-N-tert-Butoxycarbonyl-2-(N-tert-butoxycarbonyl-
4
1
0305
dx.doi.org/10.1021/jo401694e | J. Org. Chem. 2013, 78, 10298−10309

The Journal of Organic Chemistry
Article
+
acetylamidomethyl)-3,4-O-isopropylidene-5-(((1S)-1-acetoxy-3-
butenyl))pyrrolidine (16L). Alcohol 15aL (900.0 mg, 1.86 mmol) was
dissolved in dry pyridine (3 mL), and 4-dimethylaminopyridine (90
mg) followed by acetic anhydride (3.72 mmol, 0.35 mL) was added.
After being stirred at the same temperature for 1.5 h, the mixture was
concentrated at reduced pressure to remove pyridine. Then it was
extracted with EtOAc (3 × 15 mL), washed with water and brine, and
concentrated under vacuum. The residue was purified by column
chromatography on silica gel (petroleum ether/EtOAc 6:1) to afford
compound 16L (970.1 mg, 99%) as a white solid.
25.9, 24.7, 21.3, 18.3, −5.3. HRMS (ESI) m/z: [M + H] calcd for
+
C H N O Si 675.3883; found 675.3873.
32
59
2
11
3
0
Data for 18aD: [α] −23 (c 1.0, CH Cl ). HRMS (ESI) m/z: [M +
D
2
2
+
+
Na] calcd for C H N O SiNa 697.3702; found 697.3702.
32
58
2
11
3
0
−1
Data for 18bL: [α]D 0 (c 1.0, CH Cl ). IR (neat, cm ): 3459
2
2
(OH), 2932 (m), 1738 (s, CO), 1700 (s, CO), 1370 (s), 1250
1
(s), 1154 (s), 837 (s), 777 (s). H NMR (CDCl , 300 MHz): δ 5.79
3
(s, 1H), 4.74−4.71 (m, 1H), 4.33−4.28 (m, 2H), 4.01−3.94 (m, 1H),
3.89−3.85 (m, 1H), 3.76−3.60 (m, 3H), 3.46 (dd, J = 9.9 and 3.9 Hz,
1H), 2.76−2.74 (m, 1H), 2.44 (s, 3H), 2.01 (s, 3H), 1.96−1.92 (m,
31
Data for 16L: Mp 85−87 °C. [α] +10 (c 0.83, CH Cl ). IR (neat,
2H), 1.53−1.42 (m, 21H), 1.23 (s, 3H), 0.87−0.85 (m, 9H), 0.04 (s,
D
2
2
−1
13
cm ): 2918 (s), 1739 (s, CO), 1701 (s, CO), 1370 (s), 1147 (s).
6H). C NMR (CDCl , 75 MHz): δ 173.3, 170.9, 154.2, 153.0, 111.9,
3
1
H NMR (CDCl , 300 MHz): δ 5.86−5.75 (m, 1H), 5.72 (s, 1H),
83.9, 80.5, 79.9, 79.4, 70.1, 69.7, 67.1, 63.2, 62.0, 43.2, 35.4, 28.4, 28.2+,
3
5
.12−5.00 (m, 2H), 4.73−4.69 (m, 1H), 4.35−4.30 (m, 2H), 3.97 (dd,
27.1, 26.2, 26.0, 24.8, 21.5, 18.4, −5.3. HRMS (ESI) m/z: [M + H]
+
J = 13.5 and 7.8 Hz, 1H), 3.81−3.77 (m, 1H), 3.68 (dd, J = 13.5 and
.1 Hz, 1H), 2.60−2.46 (m, 2H), 2.44 (s, 3H), 1.99 (s, 3H), 1.53−1.43
m, 24H). 13C NMR (CDCl , 75 MHz): δ 173.3, 170.5, 154.3, 153.0,
calcd for C32
Data for 18bD: [α]
two steps, 18aD:18bD = 1.5:1. HRMS (ESI) m/z: [M + Na] calcd
H
59
N
O
2
11Si 675.3883; found 675.3889.
30
8
(
D 2 2
+2 (c 1.0, CH Cl ). 70% combined yield over
+
3
+
1
2
34.6, 117.3, 112.0, 83.9, 80.5, 80.0, 79.5, 70.9, 62.5, 62.0, 43.2, 36.3,
for C32H N O11SiNa 697.3702; found 697.3701.
58 2
+
8.4, 28.2, 27.1, 26.2, 24.9, 21.4. HRMS (ESI) m/z: [M + Na] calcd
Mesylation Product Precursors 19aL and 19bL. Following the
above general method for 18aL, 17L (700.0 mg, 1.33 mmol) gave
19aL (445.8 mg) and 19bL (342.9 mg) as a colorless oil in 88% total
yield from 17L.
+
for C H N O Na 549.2783; found 549.2791.
26
42
2
9
3
1
Data for 16D: 96% yield, mp 85−86 °C. [α] −8 (c 1.0, CH Cl ).
D
2
2
+
+
HRMS (ESI) m/z: [M + H] calcd for C H N O 527.2963; found
26
43
2
9
Data for 19aL: [α]2
7
+8 (c 1.0, CH Cl ). IR (neat, cm ): 3488
−1
527.2962.
D 2 2
(
2S,3S,4R,5S)-1-N-tert-Butoxycarbonyl-2-(N-tert-butoxycarbonyl-
(OH), 2932 (m), 1739 (s, CO), 1702 (s, CO), 1370 (s), 1240
1
acetylamidomethyl)-3,4-O-isopropylidene-5-(((1R)-1-acetoxy-3-
(s), 1148 (s), 837 (s), 778 (s). H NMR (CDCl , 300 MHz): δ 5.85
3
butenyl))pyrrolidine (17L). Following the above general method for
6L, homoallylic alcohol 15bL (713.0 mg, 1.5 mmol) gave 17L (740.2
(s, 1H), 4.66−4.62 (m, 1H), 4.30−4.27 (m, 1H), 4.17 (m, 1H), 3.92
(dd, J = 7.2 and 5.4 Hz, 1H), 3.75−3.71 (m, 2H), 3.57 (dd, J = 9.9 and
3.9 Hz, 1H), 3.34 (dd, J = 9.9 and 7.8 Hz, 1H), 2.63(s, 1H), 2.42 (s,
3H), 2.00 (s, 3H), 1.99−1.90 (m, 1H), 1.80 (dd, J = 11.7 and 3.9 Hz,
1H), 1.51−1.49 (m, 9H), 1.40−1.39 (m, 12H), 1.21 (s, 3H), 0.84 (s,
1
mg, 96%) as a colorless oil.
Data for 17L: [α]3 −8 (c 1.0, CH Cl ). IR (neat, cm ): 2980 (m),
1
D
−1
2
2
1
1
738 (s, CO), 1701 (s, CO), 1370 (s), 1238 (s), 1149 (s). H
9H), 0.00 (s, 6H). 13C NMR (CDCl , 75 MHz): δ 173.2, 170.7, 154.0,
NMR (CDCl , 300 MHz): δ 5.83−5.75 (m, 2H), 5.11−5.02 (m, 2H),
3
3
4
1
(
(
1
2
.67−4.63 (m, 1H), 4.35 (dd, J = 6.6 and 1.8 Hz, 1H), 4.26−4.20 (m,
H), 4.02−4.00 (m, 1H), 3.91 (dd, J = 7.5 and 5.4 Hz, 1H), 3.85−3.78
152.9, 112.1, 83.8, 80.2, 79.6, 70.4, 70.1, 67.3, 62.3, 61.2, 43.0, 34.8,
28.3, 28.0, 27.0, 26.3, 25.9, 24.6, 21.4, 18.3, −5.36, −5.4. HRMS (ESI)
+
+
m, 1H), 2.60−2.55 (m, 2H), 2.48 (s, 3H), 2.05 (s, 3H), 1.56−1.28
m/z: [M + H] calcd for C H N O Si 675.3883; found 675.3887.
32 59 2 11
m, 24H). 13C NMR (CDCl , 75 MHz): δ 172.9, 170.0, 153.7, 152.6,
27
3
Data for 19aD: [α]D −8 (c 1.0, CH Cl ). HRMS (ESI) m/z: [M +
+ +
2
2
34.5, 116.8, 111.9, 83.4, 80.2, 79.9, 79.1, 70.9, 61.9, 60.6, 42.7, 35.8,
8.1, 27.7, 26.7, 26.0, 24.4, 20.9. HRMS (ESI) m/z: [M + Na] calcd
for C H N O Na 549.2783; found 549.2788.
Data for 17D: 97% yield, [α] +8 (c 1.0, CH Cl ). HRMS (ESI)
Na] calcd for C H N O SiNa 697.3702; found 697.3702.
32 58 2 11
+
27
−1
Data for 19bL: [α]D +18 (c 1.0, CH Cl ). IR (neat, cm ): 3494
2 2
+
26
42
2
9
(OH), 2932 (m), 1738 (s, CO), 1698 (s, CO), 1370 (s), 1249
3
1
1
D
2
2
(s), 1148 (s), 837 (s), 777 (s). H NMR (CDCl , 300 MHz): δ 5.96
3
+
+
m/z: [M + H] calcd for C H N O 527.2963; found 527.2960.
(s, 1H), 4.60−4.57 (m, 1H), 4.30−4.28 (m, 1H), 4.22−4.20 (m, 1H),
26
43
2
9
General Procedure for the Synthesis of 18aL, 18bL, 19aL,
and 19bL. Mesylation Product Precursors 18aL and 18bL. To a
solution of 16L (960.0 mg, 1.83 mmol) in acetone (4 mL) were added
a catalytic amount of OsO (9.3 mL, 0.183 mmol, 0.5% in water) and
N-methylmorpholine N-oxide (357.0 mg, 1.83 mmol, 60% in water).
When the starting material had disappeared, the reaction was
quenched with sat. NaHSO solution, and the mixture was stirred
vigorously for 1 h. The solvent was removed under reduced pressure.
The residue was extracted with EtOAc (3 × 15 mL), washed with
water and brine, and concentrated under vacuum to afford an
inseparable mixture of diols (826.0 mg, 86%) as a colorless oil. The
391−3.87 (m, 2H), 3.74−3.67 (m, 1H), 3.55−3.53 (m, 1H), 3.50−
3
1
.44 (m, 2H), 2.43 (s, 3H), 2.03−1.97 (m, 4H), 1.79−1.71 (m, 1H),
13
.51−1.40 (m, 21H), 1.22 (s, 3H), 0.84 (s, 9H), 0.00 (s, 6H).
C
4
NMR (CDCl , 75 MHz): δ 172.7, 171.0, 153.9, 152.6, 111.7, 83.6,
3
8
2
0.3, 79.6, 69.7, 68.5, 67.3, 62.3, 61.1, 42.6, 35.7, 28.1, 27.8, 26.8, 26.0,
+
5.7, 24.4, 20.9, 18.1, −5.6. HRMS (ESI) m/z: [M + H] calcd for
+
3
C H N O Si 675.3883; found 675.3892.
32
59
2
11
27
Data for 19bD: [α]D −12 (c 1.0, CH Cl ). 80% combined yield
2
2
+
over two steps, 19aD:19bD = 1.3:1. HRMS (ESI) m/z: [M + H]
calcd for C H N O Si 675.3883; found 675.3876.
+
32
59
2
11
General Procedure for the Synthesis of 20L, 21L, 22L, and
23L. Cyclization Precursor 20L. To an ice-cold solution of alcohol
inseparable diol mixture was dissolved in dry CH Cl2 (10 mL).
Triethylamine (0.6 mL, 4.4 mmol) and DMAP (18.0 mg, 0.147 mmol)
2
18aL (100.0 mg, 0.15 mmol) in CH Cl2 (3 mL) was added
2
were added, followed by the addition of tert-butylchlorodimethylsilane
triethylamine (0.3 mmol, 40 μL), followed by the addition of
methanesulfonyl chloride (0.225 mmol, 20 μL) dropwise. After the
mixture was stirred for 30 min, the reaction was quenched with water
(2 mL), and the mixture was extracted with CH Cl (20 mL). The
(
444.0 mg, 2.94 mmol). After the mixture was stirred for 4 h, the
reaction was quenched with water (2 mL). CH Cl (30 mL) was
2
2
added to extract the product. Then the combined organic extracts were
2
2
washed with water and brine, dried (MgSO ), and then concentrated.
combined organic extracts were washed with water and brine, dried
4
The residue was purified by column chromatography on silica gel
(MgSO ), and then concentrated. The residue was purified by column
4
(
1
petroleum ether/EtOAc 4:1) to afford as colorless oils compounds
8aL (464.8 mg) and 18bL (387.3 mg) in 86% yield from 16L.
chromatography on silica gel (petroleum ether/EtOAc 5:1) to afford
compound 20L (102.0 mg, 92%) as a colorless oil.
Data for 20L: [α]D +2 (c 1.0, CH Cl ). IR (neat, cm ): 2934 (m),
2 2
Data for 18aL: [α]3 +20 (c 1.0, CH Cl ). IR (neat, cm ): 3508
0
−1
30
−1
D
2
2
1
(
OH), 2932, 1737 (s, CO), 1698 (s, CO), 1370 (s), 1251 (s),
1737 (s, CO), 1698 (s, CO), 1369 (s), 1250 (s), 1175 (s). H
1
1
1
3
3
1
145 (s), 937 (s), 777 (s). H NMR (CDCl , 300 MHz): δ 5.83 (s,
NMR (CDCl , 300 MHz): δ 4.77−4.71 (m, 2H), 4.34−4.32 (m, 1H),
3
3
H), 4.73−4.69 (m, 1H), 4.29−4.24 (m, 2H), 3.91−3.89 (m, 1H),
.82−3.79 (m, 1H), 3.66−3.50 (m, 2H), 3.47−3.45 (m, 2H), 3.13−
.11 (m, 1H), 2.38 (s, 3H), 2.00−1.91 (m, 4H), 1.72−1.65 (m, 1H),
4.24−4.19 (m, 1H), 4.02−3.95 (m, 1H), 3.87−3.85 (m, 1H), 3.80−
3.62 (m, 3H), 3.12−3.10 (m, 1H), 3.06 (s, 3H), 2.41 (s, 3H), 2.23−
2.14 (m, 1H), 2.07−1.93 (m, 4H), 1.51−1.41 (m, 21H), 1.21 (s, 3H),
13
13
.48−1.36 (m, 21H), 1.19 (s, 3H), 0.81 (s, 9H), −0.02 (s, 6H).
C
0.85 (s, 9H), 0.03 (s, 6H). C NMR (CDCl , 75 MHz): δ 173.2,
3
NMR (CDCl , 75 MHz): δ 173.1, 171.4, 154.1, 152.8, 111.8, 83.9,
171.1, 154.3, 152.9, 111.9, 84.0, 80.7, 80.6, 79.8, 79.1, 68.2, 65.3, 63.4,
3
80.4, 79.6, 69.3, 68.7, 67.2, 63.1, 61.8, 43.1, 35.7, 28.3, 28.1, 27.0, 26.1,
61.5, 43.3, 38.5, 31.6, 28.4, 28.1, 27.1, 26.0, 25.9, 24.5, 21.3, 18.4, −5.4.
1
0306
dx.doi.org/10.1021/jo401694e | J. Org. Chem. 2013, 78, 10298−10309

The Journal of Organic Chemistry
Article
HRMS (ESI) m/z: [M + Na]+ calcd for C H N O SSiNa
+
dissolved in MeOH (3 mL) and H O (0.5 mL). K CO (75.0 mg, 0.54
3
3
60
2
13
2
2
3
7
75.3478; found 775.3451.
Data for 20D: 90% yield, [α] −2 (c 1.0, CH Cl ). HRMS (ESI)
mmol) was added to the above solution. After the solution was stirred
at 60 °C for 4 h, the solvent was removed in vacuo. The residue was
extracted with CH Cl (3 × 10 mL), washed with water and brine,
2
2
D
2
2
+
+
m/z: [M + Na] calcd for C H N O SSiNa 775.3478; found
33
60
2
13
2
2
775.3474.
dried (MgSO ), and concentrated. The resulting residue was purified
4
Cyclization Precursor 21L. Following the above general method for
0L, compound 18bL (100.0 mg, 0.15 mmol) gave 21L (103.7 mg,
3%) as a colorless oil.
by column chromatography on silica gel (petroleum ether/EtOAc 2:1
2
9
then CH Cl /MeOH + 1% NH OH 80:1) to afford compound 24L
2
2
3
(46.2 mg, 42%) as a colorless oil.
Data for 21L: [α]3 −4 (c 1.0, CH Cl ), IR (neat, cm ): 2932 (m),
0
−1
30
−1
Data for 24L: [α] +3.5 (c 1.15, CH Cl ). IR (neat, cm ): 3296
D
2
2
D 2 2
1
(
(
739 (s, CO), 1698 (s, CO), 1370 (s), 1268 (s), 1174 (s), 1148
(br, OH), 2930 (m), 1654 (s, CO), 1377 (m), 1256 (m), 1097 (m),
1
1
s). H NMR (CDCl , 300 MHz): δ 4.73−4.69 (m, 2H), 4.34−4.29
838 (s). H NMR (CDCl
3
, 300 MHz): δ 6.21 (s, 1H), 4.56−4.53 (m,
3
m, 2H), 3.96−3.93 (m, 2H), 3.82−3.79 (m, 1H), 3.74 (dd, J = 11.7
1H), 4.39−4.37 (m, 2H), 3.70−3.61 (m, 4H), 3.50−3.49 (m, 1H),
and 6.9 Hz, 1H), 3.70−3.62 (m, 1H), 3.03 (s, 3H), 2.44 (s, 3H),
3.28−3.08 (m, 2H), 2.45 (s, 1H), 2.19 (s, 3H), 1.76−1.74 (m, 2H),
1
3
2
(
.23−2.21 (m, 2H), 2.05 (s, 3H), 1.53 (m, 9H), 1.43 (m, 12H), 1.24
1.39 (s, 3H), 1.21−1.83 (m, 3H), 0.83 (s, 9H), 0.00 (s, 6H). C NMR
s, 3H), 0.88 (s, 9H), 0.07 (s, 6H). 13C NMR (CDCl , 75 MHz): δ
(CDCl
, 75 MHz): δ 170.4, 112.2, 85.8, 79.8, 75.4, 70.7, 64.7, 62.1,
3
3
1
6
73.1, 171.0, 154.2, 153.0, 111.8, 84.1, 82.7, 80.7, 79.8, 79.7, 68.7, 64.8,
61.5, 41.4, 38.7, 26.0, 25.9, 24.1, 23.4, 18.3, −5.4. HRMS (ESI) m/z:
+
+
3.4, 62.3, 42.9, 38.5, 28.4, 28.2, 27.2, 26.0, 24.6, 21.4, 18.5, −5.3.
[M + H] calcd for C20
H N O Si 415.2623; found 415.2623.
39 2 5
+
+
30
HRMS (ESI) m/z: [M + Na] calcd for C H N O SSiNa
Data for 24D: 38% yield, [α] Cl
m/z: [M + H] calcd for C20H N O Si 415.2623; found 415.2623.
39 2 5
D
−6 (c 1.0, CH
2
2
). HRMS (ESI)
3
3
60
2
13
+
+
7
75.3478; found 775.3477.
Data for 21D: 89% yield, [α] +2 (c 1.0, CH Cl ). HRMS (ESI)
2
2
(1S,3S,5S,6S,7R,7aS)-1-Hydroxy-3-((tert-butyldimethylsilyl)oxy)-
methyl-5-acetamidomethyl-6,7-O-isopropylidenepyrrolizidine
D
2
2
+
+
m/z: [M + Na] calcd for C H N O SSiNa 775.3478; found
33
60
2
13
(
(
25L). Following the above general method for 20L, compound 21L
7
75.3475.
200.0 mg, 0.15 mmol) gave 25L (46.2 mg, 42%) as a colorless oil.
Cyclization Precursor 22L. Following the above general method for
0L, compound 19aL (200.0 mg, 0.3 mmol) gave 22L (210.2 mg,
5%) as a colorless oil.
Data for 25L: [α]3 −1.5 (c 1.3, CH Cl ). IR (neat, cm ): 3310
0
−1
2
D
2
2
(
br, OH), 2930 (m), 1656 (s, CO), 1547 (m), 1374 (m), 1256 (m),
9
1
Data for 22L: [α]3 +18 (c 1.0, CH Cl ). IR (neat, cm ): 2934
0
D
−1
1209 (m), 1081 (m), 837 (s). H NMR (CDCl , 300 MHz): δ 6.25 (s,
3
2
2
1
H), 4.54−4.51 (m, 1H), 4.33−4.32 (m, 2H), 3.51−3.32 (m, 7H),
(
m), 1739 (s, CO), 1699 (s, CO), 1370 (s), 1219 (s), 1174 (s).
1
2.72−2.63 (m, 1H), 2.51−2.41 (m, 1H), 1.87 (s, 3H), 1.50−1.45 (m,
H NMR (CDCl , 300 MHz): δ 4.71−4.61 (m, 2H), 4.33−4.31 (m,
3
13
1
H), 1.34 (s, 3H), 1.36 (s, 3H), 0.82 (s, 9H), 0.00 (s, 6H). C NMR
1
H), 4.24−4.22 (m, 1H), 3.90−3.87 (m, 3H), 3.74−3.64 (m, 2H),
.14−3.12 (m, 1H), 3.06 (s, 3H), 2.46 (s, 3H), 2.41−2.31 (m, 1H),
.10 (s, 3H), 2.07−2.00 (m, 1H), 1.54 (s, 9H), 1.45 (s, 12H), 1.26 (s,
(
CDCl , 75 MHz): δ 170.1, 112.1, 86.1, 81.5, 75.8, 72.1, 69.0, 68.4,
3
3
2
3
6
6.4, 40.9, 38.5, 26.3, 26.0, 25.8, 23.5, 23.3, 18.5, −5.2. HRMS (ESI)
+
+
1
3
m/z: [M + H] calcd for C20
H
39
N
2
O
5
Si 415.2623; found 415.2625.
H), 0.88 (s, 9H), 0.06−0.05 (m, 6H). C NMR (CDCl , 75 MHz):
3
30
Data for 25D: 41% yield, [α]D +2 (c 1.5, CH Cl ). HRMS (ESI)
2
2
δ 172.9, 170.6, 154.0, 152.7, 111.7, 84.0, 83.4, 80.4, 79.6, 79.5, 69.9,
+
+
m/z: [M + H] calcd for C H N O Si 415.2623; found 415.2625.
2
0
39
2
5
6
2
5.0, 62.3, 60.2, 42.8, 38.1, 33.8, 31.6, 28.2, 27.9, 27.0, 26.1, 25.8, 24.3,
+
(1R,3R,5S,6S,7R,7aS)-1-Hydroxy-3-((tert-butyldimethylsilyl)oxy)-
1.1, 18.3, −5.6, −5.7. HRMS (ESI) m/z: [M + Na] calcd for
methyl-5-acetamidomethyl-6,7-O-isopropylidenepyrrolizidine
+
C H N O SSiNa 775.3478; found 775.3478.
33
60
2
13
(
(
26L). Following the above general method for 20L, compound 22L
200.0 mg, 0.15 mmol) gave 26L (47.3 mg, 43%) as a colorless oil.
2
2
Data for 22D: 97% yield, [α] −16 (c 1.0, CH Cl ). HRMS (ESI)
D
2
2
+
+
m/z: [M + Na] calcd for C H N O SSiNa 775.3478; found
3
3
60
2
13
Caution: compound 26L was poorly stable under conditions for
removal of the solvent MeOH. Thus, no heat should be applied
while the reaction mixture is concentrated, and it should be used
directly in the next step.
7
75.3474.
Cyclization Precursor 23L. Following the above general method for
0L, compound 19bL (485.0 mg, 0.72 mmol) gave 23L (501.3 mg,
3%) as a colorless oil.
2
9
(
1R,3S,5S,6S,7R,7aS)-1-Hydroxy-3-((tert-butyldimethylsilyl)oxy)-
Data for 23L: [α]3 +14 (c 1.0, CH Cl ). IR (neat, cm ): 2932
0
D
−1
2
2
methyl-5-acetamidomethyl-6,7-O-isopropylidenepyrrolizidine
(27L). Following the above general method for 20L, compound 23L
(200.0 mg, 0.15 mmol) gave 27L (44.2 mg, 40.2%) as a colorless oil.
(
m), 1737 (s, CO), 1698 (s, CO), 1369 (s), 1249 (s), 1174 (s).
1
H NMR (CDCl , 300 MHz): δ 4.74−4.72 (m, 1H), 4.67−4.63 (m,
3
Data for 27L: [α]3 +20 (c 0.8, CH Cl ). IR (neat, cm ): 3310 (br,
0
−1
1
H), 4.35 (dd, J = 6.4 and 1.7 Hz, 1H), 4.25−4.17 (m, 1H), 3.97−3.95
m, 2H), 3.83−3.73 (m, 3H), 3.15−3.13 (m, 1H), 3.09 (s, 3H), 2.47
s, 3H), 2.43−2.37 (m, 1H), 2.10 (s, 3H), 2.08−2.02 (m, 1H), 1.55 (s,
D 2 2
(
(
9
OH), 2929 (m), 1656 (s, CO), 1549 (m), 1374 (m), 1257 (m),
1
1210 (m), 1083 (m), 837 (s). H NMR (CDCl , 300 MHz): δ 6.41 (s,
3
13
H), 1.47 (s, 12H), 1.27 (s, 3H), 0.89 (s, 9H), 0.07−0.06 (m, 6H). C
1H), 4.70−4.66 (m, 1H), 4.54−4.51 (m, 1H), 4.41 (dd, J = 6.0 and 3.0
Hz, 1H), 3.47−3.44 (m, 1H), 3.41−3.33 (m, 2H), 3.31−3.28 (m, 2H),
3.26−3.17 (m, 1H), 3.07−2.98 (m, 1H), 2.14 (s, 1H), 2.07−1.98 (m,
NMR (CDCl , 75 MHz): δ 172.8, 170.4, 153.8, 152.6, 111.7, 83.7,
3
8
0.3, 79.7, 79.4, 68.6, 65.1, 61.9, 60.0, 42.7, 38.1, 32.5, 31.4, 28.1, 27.7,
+
2
6.8, 26.0, 25.6, 24.3, 20.9, 18.0, −5.7. HRMS (ESI) m/z: [M + Na]
1H), 1.89 (s, 3H), 1.72−1.64 (m, 1H), 1.46 (s, 3H), 1.23 (s, 3H), 0.83
+
13
calcd for C H N O SSiNa 775.3478; found 775.3477.
(s, 9H), 0.00 (s, 6H). C NMR (CDCl , 75 MHz): δ 170.2, 113.0,
33
60
2
13
3
2
2
Data for 23D: 95% yield, [α] −10 (c 1.0, CH Cl ). HRMS (ESI)
85.6, 82.3, 73.3, 69.9, 69.1, 68.8, 64.5, 40.4, 38.6, 26.6, 26.0, 23.8, 23.3,
D
2
2
+
+
+
+
m/z: [M + Na] calcd for C H N O SSiNa 775.3478; found
18.5, −5.1. HRMS (ESI) m/z: [M + H] calcd for C H N O Si
3
3
60
2
13
20 39
2
5
7
75.3474.
General Procedure for the Synthesis of Protected Pyrroli-
zidines 24L, 25L, 26L, and 27L. (1S,3R,5S,6S,7R,7aS)-1-Hydroxyl-
-((tert-butyldimethylsilyl)oxy)methyl-5-acetamidomethyl-6,7-O-
isopropylidenepyrrolizidine (24L). To a solution of compound 20L
415.2623; found 415.2622.
3
0
Data for 27D: 43% yield, [α]
−22 (c 1.2, CH Cl ). HRMS (ESI)
2 2
m/z: [M + H] calcd for C H N O Si 415.2623; found 415.2622.
D
+
+
20
39
2
5
3
General Procedure for the Synthesis of (−)-Pochonicine
(1L), (−)-3-epi-Pochonicine (2L), (−)-1-epi-Pochonicine (3L),
and (−)-1,3-Di-epi-pochonicine (4L). (−)-Pochonicine (1L). To a
solution of compound 24L (40.0 mg, 0.0967 mmol) in MeOH (0.5
mL) was added 6 N HCl (1.5 mL). After the mixture was stirred for 12
h, the solvent was removed, and the residue was dissolved in MeOH,
neutralized with aqueous ammonium solution, and concentrated in
vacuo. The above procedure was repeated three times to ensure
complete neutralization. The residue was purified by an acid resin
column (DOWEX 50W × 8, 100−200 mesh), eluting with distilled
(
(
200.0 mg, 0.27 mmol) in dry CH Cl (8 mL) was added p-cresol
2 2
287.0 mg, 3.24 mmol) and anhydrous ZnBr [410.0 mg, 1.83 mmol;
2
prepared by dissolution of 25 g of ZnBr ·7H O in 500 mL of THF
2
2
(
dried over 4 Å MS) for 2 days followed by removal of the solvent in
vacuo]. After the mixture was stirred for 12 h, the reaction was
quenched with sat. NaHCO3 (3 mL). The reaction mixture was
filtered through Celite, and the filtrate was extracted with CH Cl (3 ×
2
2
10 mL). The combined organic extracts were washed with water and
brine, dried (MgSO ), and then concentrated. The residue was
water (20 mL) and then 1 N NH OH (50 mL), affording 1L (24.6
4
4
subjected to the next step without further purification. The residue was
mg, 98%) as light-yellow oil.
1
0307
dx.doi.org/10.1021/jo401694e | J. Org. Chem. 2013, 78, 10298−10309

The Journal of Organic Chemistry
Article
Data for 1L: [α]35 −1.07 (c 0.90, MeOH). IR (neat, cm ): 3308
−1
Data for 3L: [α] 1D 5 −10 (c 0.6, MeOH). IR (neat, cm ): 3299 (br,
−1
D
1
1
(
4
=
3
1
7
br, OH), 2930 (m), 1650 (s, CO). H NMR (300 MHz, D O): δ
OH), 2928 (m), 1648 (s, CO), 1129 (m). H NMR (CD OD, 300
2
3
.56 (dd, J = 11.8 and 6.5 Hz, 1H), 4.14 (t, J = 4.0 Hz, 1H), 3.94 (dd, J
MHz): δ 4.42 (dd, J = 10.3 and 5.4 Hz, 1H), 4.19 (t, J = 4.0 Hz, 1H),
3.98 (dd, J = 11.7 and 7.2 Hz, 1H), 3.78 (dd, J = 7.5 and 3.9 Hz, 1H),
8.1 and 4.0 Hz, 1H), 3.78−3.75 (m, 2H), 3.49−3.43 (m, 1H), 3.39−
.36 (m, 2H), 3.25−3.18 (m, 1H), 2.12 (dt, J = 12.5 and 6.0 Hz, 1H),
3
.71 (dd, J = 11.4 and 3.9 Hz, 1H), 3.52−3.47 (m, 2H), 3.44−3.38 (m,
13
.99−1.90 (m, 4H). C NMR (75 MHz, D O): δ 174.4, 76.7, 73.3,
2
2H), 3.33−3.25 (m, 1H), 2.15−2.05 (m, 1H), 1.95 (s, 3H), 1.86 (dt, J
0.0, 68.1, 60.9, 59.2, 57.3, 42.0, 37.7, 21.9. HRMS (ESI) m/z: [M +
13
=
12.0 and 6.0 Hz, 1H). C NMR (CD OD, 75 MHz): δ 173.6, 78.8,
3
+
+
H] calcd for C H N O 261.1445; found 261.1442.
11
21
2
5
74.0, 73.8, 68.9, 63.4, 62.4, 61.5, 43.8, 40.9, 22.6. HRMS (ESI) m/z:
M + H] calcd for C H N O 261.1445; found 261.1445.
1
Additional NMR data for 1L: H NMR (300 MHz, CD OD): δ
+
+
3
[
11 21 2 5
4
=
5
(
2
7
.56 (dd, J = 10.9 and 6.1 Hz, 1H), 4.00 (t, J = 3.9 Hz, 1H), 3.84 (dd, J
8.0 and 3.9 Hz, 1H), 3.80 (d, J = 3.4 Hz, 1H), 3.67 (dd, J = 11.9 and
15
−1
Data for 3D: 96% yield, [α]D +12 (c 0.5, MeOH). IR (neat, cm ):
1
3
307 (br, OH), 2930 (m), 1651 (s, CO), 1133 (m). H NMR (300
.4 Hz, 1H), 3.59−3.54 (m, 1H), 3.47 (t, J = 4.2 Hz, 1H), 3.42−3.41
MHz, CD OD): δ 4.46 (dd, J = 10.8 and 5.1 Hz, 1H), 4.21 (t, J = 4.0
3
m, 2H), 3.34−3.32 (m, 1H), 2.14 (dt, J = 12.4 and 6.1 Hz, 1H),
Hz, 1H), 4.00 (dd, J = 12.0 and 7.5 Hz, 1H), 3.83 (dd, J = 7.8 and 3.9
Hz, 1H), 3.76 (dd, J = 12.0 and 3.9 Hz, 1H), 3.58 (m, 2H), 3.49−3.44
13
.02−1.98 (m, 4H). C NMR (75 MHz, CD OD): δ 174.1, 78.2, 75.9,
3
1.8, 69.2, 63.2, 62.2, 61.1, 42.6, 39.9, 22.6
1
8
(m, 2H), 3.40−3.35 (m, 1H), 2.14 (dt, J = 12.6 and 6.3 Hz, 1H), 2.01
Data for 1D: 95% yield, [α] +0.74 (c 0.70, MeOH). IR (neat,
D
13
−1
1
(s, 3H), 1.97−1.88 (m, 1H). C NMR (75 MHz, CD
3
OD): δ 173.7,
cm ): 3313 (br, OH), 2931 (m), 1646 (s, CO). H NMR (300
7
8.7, 73.9, 73.7, 68.9, 63.3, 62.5, 61.6, 43.6, 40.8, 22.6. HRMS (ESI)
m/z: [M + H] calcd for C H N O 261.1445; found 261.1443.
−)-1,3-Di-epi-pochonicine (4L). Following the above general
method for 24L, compound 27L (45.0 mg, 0.11 mmol) gave 4L
MHz, D O): δ 4.53 (dd, J = 12.0 and 6.6 Hz, 1H), 4.12 (t, J = 3.9 Hz,
2
+
+
1
(
H), 3.91 (dd, J = 8.1 and 3.9 Hz, 1H), 3.75−3.73 (m, 2H), 3.45−3.41
11 21
2
5
(
m, 1H), 3.38−3.31 (m, 3H), 3.25−3.13 (m, 1H), 2.11 (dt, J = 12.8
13
and 6.2 Hz, 1H), 1.97 (s, 3H), 1.94−1.88 (m, 1H). C NMR (75
(
27.8 mg, 98%) as a colorless oil.
MHz, D O): δ 174.4, 76.5, 73.3, 69.9, 68.0, 61.0, 60.8, 59.1, 41.8, 37.6,
2
Data for 4L: [α]1 −1.6 (c 1.2, MeOH). IR (neat, cm ): 3306 (br,
5
−1
+
+
2
1.8. HRMS (ESI) m/z: [M + H] calcd for C H N O 261.1445;
D
11
21
2
5
1
found 261.1445.
OH), 2928 (m), 1648 (s, CO), 1134 (m). H NMR (300 MHz,
1
Additional NMR data for 1D: H NMR (300 MHz, CD OD): δ
CD
3
OD): δ 4.43 (dd, J = 8.2 and 4.8 Hz, 1H), 4.27 (t, J = 5.2 Hz, 1H),
3
4
.56 (dd, J = 12.0 and 6.6 Hz, 1H), 3.97 (t, J = 3.9 Hz, 1H), 3.83 (dd, J
8.0 and 3.9 Hz, 1H), 3.78 (d, J = 3.3 Hz, 1H), 3.64 (dd, J = 12.0 and
3.77 (dd, J = 6.3 and 5.0 Hz, 1H), 3.55−3.51 (m, 1H), 3.48 (d, J = 4.2
Hz, 1H), 3.39 (dd, J = 10.9 and 6.1 Hz, 1H), 3.32−3.23 (m, 3H), 3.02
(dd, J = 11.7 and 5.4 Hz, 1H), 2.01 (ddd, J = 12.0, 6.0, and 3.0 Hz,
=
5
.1 Hz, 1H), 3.52−3.48 (m, 1H), 3.40−3.35 (m, 3H), 3.27−3.22 (m,
13
13
1H), 2.11 (dt, J = 12.0 and 6.0 Hz, 1H), 2.00−1.92 (m, 4H).
C
1H), 1.95 (s, 3H), 1.74 (ddd, J = 12.0, 6.0, and 3.0 Hz, 1H). C NMR
NMR (75 MHz, CD OD): δ 173.9, 78.4, 75.6, 71.8, 69.2, 62.8, 62.4,
(75 MHz, CD OD): δ 173.5, 76.7, 74.3, 74.0, 71.4, 70.7, 68.4, 66.5,
3
3
+
+
6
0.9, 42.8, 40.0, 22.6
Data for natural pochonicine (supplied by Nitoda): H NMR (300
MHz, D O): δ 4.56 (dd, J = 11.7 and 6.5 Hz, 1H), 4.15 (t, J = 4.1 Hz,
4
3.1, 39.9, 22.6. HRMS (ESI) m/z: [M + H] calcd for C H N O
11 21 2 5
1
2
61.1445; found 261.1445.
Data for 4D: 95% yield, [α]D +3.4 (c 0.7, MeOH). IR (neat, cm ):
15
−1
2
1
=
H), 3.95 (dd, J = 8.1 and 3.9 Hz, 1H), 3.78−3.76 (m, 2H), 3.47 (t, J
1
3
316 (br, OH), 2931 (w), 1647 (s, CO), 1126 (m). H NMR (300
5.6 Hz, 1H), 3.41−3.35 (m, 3H), 3.23 (dd, J = 13.6 and 5.8 Hz, 1H),
MHz, CD OD): δ 4.48−4.47 (m,1H), 4.30 (t, J = 6.0 Hz, 1H), 3.81 (t,
3
13
2
.14 (dt, J = 12.8 and 6.1 Hz, 1H), 2.00−1.91 (m, 4H). C NMR (75
J = 6.0 Hz, 1H), 3.62−3.56 (m, 1H), 3.54−3.52 (m, 1H), 3.47−3.41
MHz, D O): δ 174.5, 76.5, 73.4, 69.9, 68.0, 61.0, 60.8, 59.2, 41.8, 37.6,
2
(
(
m, 1H), 3.37−3.34 (m, 3H), 3.10 (dd, J = 11.1 and 5.4 Hz, 1H), 2.06
ddd, J = 12.0, 6.0, and 3.0 Hz, 1H), 1.97 (s, 3H), 1.79 (ddd, J = 12.0,
2
1.8
Additional data for natural pochonicine (supplied by Nitoda): H
NMR (300 MHz, CD OD): δ 4.60 (dd, J = 11.8 and 6.7 Hz, 1H), 4.01
1
13
6
.0, and 3.0 Hz, 1H). C NMR (75 MHz, CD OD): δ 173.7, 76.6,
3
3
7
4.1, 73.9, 71.5, 70.8, 68.7, 66.2, 42.8, 39.8, 22.6. HRMS (ESI) m/z:
(
t, J = 3.8 Hz, 1H), 3.87 (dd, J = 7.8 and 3.9 Hz, 1H), 3.81 (d, J = 3.6
+
+
[
M + H] calcd for C H N O 261.1445; found 261.1445.
11 21 2 5
Hz, 1H), 3.68 (dd, J = 12.0 and 5.1 Hz, 1H), 3.56−3.46 (m, 1H),
Assay of Glycosidase Inhibition. α-L-Rhamnosidase from P.
3
2
1
.44−3.41 (m, 2H), 3.40−3.38 (m, 1H), 3.31−3.25 (m, 1H), 2.19−
13
decumbens; β-N-acetylglucosaminidases from A. oryzae bovine liver,
human placenta, and jack bean; α-N-acetylgalactosaminidase from
chicken liver; and β-N-acetylgalactosaminidases from A. oryzae were
purchased from a commercial supplier. The human promyelocytic
leukemia cell line, HL-60, was provided by the RIKEN BRC through
the National Bio-Resource Project of the MEXT, Japan. The
glycosidase activities were determined using an appropriate p-
nitrophenyl glycoside as the substrate. The reaction was stopped by
.11 (m, 1H), 2.00−1.91 (m, 4H) C NMR (75 MHz, CD OD): δ
3
73.7, 78.8, 75.4, 72.1, 69.2, 62.8, 61.5, 60.8, 43.1, 40.2, 22.6
(
−)-3-epi-Pochonicine (2L). Following the above general method
for 24L, compound 25L (40.0 mg, 0.097 mmol) gave 2L (24.1 mg,
9
6%) as a colorless oil.
Data for 2L: [α]3 +6 (c 1.0, MeOH). IR (neat, cm ): 3316 (br,
0
−1
D
1
OH), 2930 (w), 1637 (s, CO). H NMR (300 MHz, CD OD): δ
3
4.53 (ddd, J = 3.4, 5.1, and 6.4 Hz, 1H), 3.95 (t, J = 3.9 Hz, 1H), 3.77
(
3
dd, J = 8.6 and 3.9 Hz, 1H), 3.57−3.44 (m, 2H), 3.37−3.34 (m, 2H),
adding 400 mM Na CO . The released p-nitrophenol was measured
spectrometrically at 400 nm.
2 3
.40−3.37 (m, 2H), 3.31−3.29 (m, 1H), 3.09−3.00 (m, 1H), 2.85−
.79 (m, 1H), 2.24 (dt, J = 13.8 and 7.0 Hz, 1H), 1.96 (s, 3H), 1.62
2
(
dt, J = 11.6 and 5.8 Hz, 1H). 13C NMR (75 MHz, CD OD): δ 173.6,
3
ASSOCIATED CONTENT
7
7.3, 76.2, 72.6, 71.6, 70.0, 69.5, 66.7, 42.8, 39.1, 22.6. HRMS (ESI)
■
+
+
m/z: [M + H] calcd for C H N O 261.1445; found 261.1445.
*
S
Supporting Information
H NMR and 13C NMR spectra for all new compounds. This
11
21
2
5
32
−1
Data for 2D: 93% yield, [α]D −5.3 (c 1.5, MeOH). IR (neat, cm ):
319 (br, OH), 2932 (m), 1638 (s, CO). H NMR (300 MHz,
1
1
3
material is available free of charge via the Internet at http://
pubs.acs.org.
CD OD): δ 4.57 (ddd, J = 3.4, 5.0, and 6.5 Hz, 1H), 3.99 (t, J = 3.9
Hz, 1H), 3.81 (dd, J = 8.7 and 3.6 Hz, 1H), 3.62−3.55 (m, 2H), 3.44−
3
8
1
1
3
.43 (m, 2H), 3.39−3.35 (m, 1H), 3.16−3.13 (m, 1H), 2.92 (dt, J =
.9 and 4.7 Hz, 1H), 2.29 (dt, J = 13.3 and 7.0 Hz, 1H), 1.98 (s, 3H),
AUTHOR INFORMATION
.66 (dt, J = 11.4 and 5.8 Hz, 1H). 13C NMR (75 MHz, CD OD): δ
■
3
73.9, 76.9, 76.5, 72.4, 71.4, 70.7, 69.7, 65.9, 42.3, 39.0, 22.6. HRMS
Corresponding Authors
+
+
(
ESI) m/z: [M + H] calcd for C H N O 261.1445; found
*E-mail: yucy@iccas.ac.cn.
11
21
2
5
2
61.1445.
−)-1-epi-Pochonicine (3L). Following the above general method
for 24L, compound 26L (36.0 mg, 0.087 mmol) gave 3L (21.3 mg,
4%) as a colorless oil.
*
E-mail: kato@med.u-toyama.ac.jp.
(
Notes
9
The authors declare no competing financial interest.
1
0308
dx.doi.org/10.1021/jo401694e | J. Org. Chem. 2013, 78, 10298−10309

The Journal of Organic Chemistry
Article
(
11) (a) Jenkinson, S. F.; Best, D.; Saville, A. W.; Mui, J.; Martinez, R.
ACKNOWLEDGMENTS
■
F.; Nakagawa, S.; Kunimatsu, T.; Alonzi, D. S.; Butters, T. D.; Norez,
C.; Becq, F.; Bleriot, Y.; Wilson, F. X.; Weymouth-Wilson, A. C.; Kato,
A.; Fleet, G. W. J. Org. Chem. 2013, 78, 7380. (b) Glawar, A. F. G.;
Best, D.; Ayers, B. J.; Miyauchi, S.; Nakagawa, S.; Aguilar-Moncayo,
This article is dedicated to Professor Zhi-Tang Huang on the
occasion of his 85th birthday. This work was supported by the
National Basic Research Program of China (2012CB822101
and 2011CB808603), the National Natural Science Foundation
of China (21272240 and 21102149), a Grant-in-Aid for
Scientific Research (C) (23590127 to A.K.) from the Japanese
Society for the Promotion of Science (JSPS) and Summit PLC
M.; García Fernan
T. D.; Wilson, F. X.; Kato, A.; Fleet, G. W. J. Chem.Eur. J. 2012, 18,
341. (c) Hu, X.-G.; Bartholomew, B.; Nash, R. J.; Wilson, F. X.; Fleet,
́
dez, J. M.; Ortiz Mellet, C.; Crabtree, E. V.; Butters,
9
G. W. J.; Nakagawa, S.; Kato, A.; Jia, Y.-M.; van Well, R.; Yu, C.-Y. Org.
Lett. 2010, 12, 2562 and references cited therein. (d) Best, D.; Wang,
C.; Weymouth-Wilson, A. C.; Clarkson, R. A.; Wilson, F. X.; Nash, R.
J.; Miyauchi, S.; Kato, A.; Fleet, G. W. J. Tetrahedron: Asymmetry 2010,
21, 311 and references cited therein. (e) D’Alonzo, D.; Guaragna, A.;
Palumbo, G. Curr. Med. Chem. 2009, 16, 473.
(
UK), and the Leverhulme Trust (G.W.J.F.).
REFERENCES
■
(
1) Usuki, H.; Toyo-oka, M.; Kanzaki, H.; Okuda, T.; Nitoda, T.
Bioorg. Med. Chem. 2009, 17, 7248.
2) (a) Horsch, M.; Mayer, C.; Sennhauser, U.; Rast, D. M.
Pharmacol. Ther. 1997, 76, 187. (b) Merzendorfer, H.; Zimoch, L. J.
Exp. Biol. 2003, 206, 4393. (c) Rast, D. M.; Baumgartner, D.; Mayer,
C.; Hollenstein, G. O. Phytochemistry 2004, 64, 339.
(
(
12) Yu, C.-Y.; Fu, Y. Acta Crystallogr. 2006, E62, o3172.
13) (a) Merino, P.; Tejero, T.; Revuelta, J.; Romero, P.; Cicchi, S.;
(
Mannucci, V.; Brandi, A.; Goti, A. Tetrahedron: Asymmetry 2003, 14,
67. (b) Tsou, E.-L.; Yeh, Y.-T.; Liang, P.-H.; Cheng, W.-C.
Tetrahedron 2009, 65, 93.
3
(
(
(
14) Holzapfel, C. W.; Crous, R. Heterocycles 1998, 48, 1337.
15) Burk, M. J.; Allen, J. G. J. Org. Chem. 1997, 62, 7054.
16) (a) Stafford, J. A.; Brackeen, M. F.; Karanewsky, D. S.; Valvano,
(
6
3) (a) Wells, L.; Vosseller, K.; Hart, G. W. Cell. Mol. Life Sci. 2003,
0, 222. (b) Buse, M. G. Am. J. Physiol.: Endocrinol. Metab. 2006, 290,
E1. (c) Slamova, K.; Bojarova, P.; Petraskova, L.; Kren, V. Biotechnol.
Adv. 2010, 28, 682.
4) (a) Hart, G. W.; Housley, M. P.; Slawson, C. Nature 2007, 446,
017. (b) Macauley, M. S.; He, Y.; Gloster, T. M.; Stubbs, K. A.;
Davies, G. J.; Vocadlo, D. J. Chem. Biol. 2010, 17, 937.
5) Vosseller, K.; Wells, L.; Lane, M. D.; Hart, G. W. Proc. Natl. Acad.
Sci. U.S.A. 2002, 99, 5313.
6) (a) Yuzwa, S. A.; Macauley, M. S.; Heinonen, J. E.; Shan, X.;
́
́
́
́
́
̌
N. L. Tetrahedron Lett. 1993, 34, 7873. (b) Apelqvist, T.; Wensbo, D.
Tetrahedron Lett. 1996, 37, 1471. (c) Kotsuki, H.; Ohishi, T.; Araki, T.;
Arimura, K. Tetrahedron Lett. 1998, 39, 4869. (d) Siro, J. G.; Martín, J.;
(
1
García-Navío, J.; Remuin
̃
an, M. J.; Vaquero, J. J. Synlett 1998, 147.
e) Yadav, J. S.; Subba Reddy, B. V.; Reddy, K. S. Synlett 2002, 468.
f) Hernandez, J. N.; Crisostomo, F. R. P.; Martín, T.; Martín, V. S.
(
(
(
́
́
Eur. J. Org. Chem. 2007, 5050. (g) Singh, O. V.; Han, H. Tetrahedron
Lett. 2007, 48, 7094. (h) Fujiwara, T.; Seki, T.; Miura, M.; Takeuchi, Y.
Heterocycles 2009, 79, 427.
(
(
(
(
Dennis, R. J.; He, Y.; Whitworth, G. E.; Stubbs, K. A.; McEachern, E.
J.; Davies, G. J.; Vocadlo, D. J. Nat. Chem. Biol. 2008, 4, 483.
b) Yuzwa, S. A.; Vocadlo, D. J. Curr. Alzheimer Res. 2009, 6, 451.
7) (a) Woynarowska, B.; Wikiel, H.; Sharma, M.; Fleet, G. W. J.;
17) Mirrington, R. N.; Schmalzl, K. J. J. Org. Chem. 1972, 37, 2877.
18) Blickenstaff, R. T. J. Am. Chem. Soc. 1960, 82, 3673.
19) Ikota, N.; Hanaki, A. Chem. Pharm. Bull. 1990, 38, 2712.
(
(
Bernacki, R. J. Anticancer Res. 1992, 12, 161. (b) Woynarowska, B.;
Wikiel, H.; Sharma, M.; Fleet, G. W. J.; Bernacki, R. J. Proc. Am. Assoc.
Cancer Res. 1989, 30, 91. (c) Ma, Z.; Vosseller, K. Amino Acids 2013,
(20) Randazzo, G.; Capasso, R.; Rosaria Cicala, M.; Evidente, A.
Carbohydr. Res. 1980, 85, 298.
(21) Yadav, J. S.; Subba Reddy, B. V. Carbohydr. Res. 2000, 329, 885.
(22) Yadav, J. S.; Reddy, B. V. S.; Srinivas, R.; Maiti, A. J. Chem. Res.
2001, 528.
4
(
5, 719.
8) Kitamura, Y.; Koshino, H.; Nakamura, T.; Tsuchida, A.; Nitoda,
T.; Kanzaki, H.; Matsuoka, K.; Takahashi, S. Tetrahedron Lett. 2013,
4, 1456.
9) For examples of opposite signs for the optical rotations of the free
base and the hydrogen chloride salt of iminosugar alkaloids, see:
a) Nash, R. J.; Fellows, L. E.; Dring, J. V.; Fleet, G. W. J.; Girdhar, A.;
(23) Bessodes, M.; Komiotis, D.; Antonakis, K. Tetrahedron Lett.
1986, 27, 579.
5
(
(24) Petrier, C.; Luche, J. L. J. Org. Chem. 1985, 50, 910.
(25) (a) Nigama, S. C.; Mann, A.; Taddei, M.; Wermutha, C.-G.
Synth. Commun. 1989, 19, 3139. (b) Donohoe, T. J.; Thomas, R. E.;
Cheeseman, M. D.; Rigby, C. L.; Bhalay, G.; Linney, I. D. Org. Lett.
2008, 10, 3615.
(26) Davis, B.; Bell, A. A.; Nash, R. J.; Watson, A. A.; Griffiths, R. C.;
Jones, M. G.; Smith, C.; Fleet, G. W. J. Tetrahedron Lett. 1996, 37,
8565.
(
Ramsden, N. G.; Peach, J. M.; Hegarty, M. P.; Scofield, A. M.
Phytochemistry 1990, 29, 111. (b) Zou, W.; Szarek, W. A. Carbohydr.
Res. 1993, 242, 311. (c) Restorp, P.; Fischer, A.; Somfai, P. J. Am.
Chem. Soc. 2006, 128, 12646. (d) Merino, P.; Delso, I.; Tejero, T.;
Cardona, F.; Marradi, M.; Faggi, E.; Parmeggiani, C.; Goti, A. Eur. J.
Org. Chem. 2008, 2929. (e) Fleet, G. W. J.; Ramsden, N. G.; Nash, R.
J.; Fellows, L. E.; Jacob, G. S.; Molyneux, R. J.; Dibello, I. C.;
Winchester, B. Carbohydr. Res. 1990, 205, 269.
(
̊
27) Hakansson, A. E.; van Ameijde, J.; Horne, G.; Nash, R. J.;
Wormald, M. R.; Kato, A.; Besra, G. S.; Gurcha, S.; Fleet, G. W. J.
Tetrahedron Lett. 2008, 49, 179.
(
10) For recent reviews of cyclic nitrones, see: (a) Brandi, A.;
Cardona, F.; Cicchi, S.; Cordero, F. M.; Goti, A. Chem.Eur. J. 2009,
15, 7808. (b) Revuelta, J.; Cicchi, S.; Goti, A.; Brandi, A. Synthesis
2
007, 485. For recent applications of cyclic nitrones in the synthesis
of pyrrolizidines, see: (c) Podolan, G.; Klescikova, L.; Fisera, L.;
Kozfsek, J.; Fronc, M. Synlett 2011, 1668. (d) Delso, I.; Tejero, T.;
Goti, A.; Merino, P. Tetrahedron 2010, 66, 1220. (e) Stecko, S.;
Solecka, J.; Chmielewski, M. Carbohydr. Res. 2009, 344, 167. (f) Stecko,
S.; Jurczak, M.; Urbanczyk-Lipkowska, Z.; Solecka, J.; Chmielewski, M.
Carbohydr. Res. 2008, 343, 2215. (g) Kaliappan, K. P.; Das, P. Synlett
2
008, 841. (h) Argyropoulos, N. G.; Panagiotidis, T.; Coutouli-
Argyropoulou, E.; Raptopoulou, C. Tetrahedron 2007, 63, 321.
i) Desvergnes, S.; Py, S.; Vallee, Y. J. Org. Chem. 2005, 70, 1459.
(
For the work of our group based on cyclic nitrones, see: (j) Zhao, W.-
B.; Nakagawa, S.; Kato, A.; Adachi, I.; Jia, Y.-M.; Hu, X.-G.; Fleet, G.
W. J.; Wilson, F. X.; Horne, G.; Yoshihara, A.; Izumori, K.; Yu, C.-Y. J.
Org. Chem. 2013, 78, 3208 and references cited therein.
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