A General Strategy for the Stereoselective Synthesis of Pyrrole-Fused Chiral Skeletons: [3+2] Cycloaddition with 2-Nitro-2,3-Unsaturated Glycosides

Article abstract of DOI:10.1002/cctc.202100795

In this study, a two-step methodology was developed for the synthesis of chiral pyrroles from 2-nitroglycals via Ferrier rearrangement and Barton-Zard reaction under mild conditions without transition metal catalysts. The Ferrier rearrangement reaction of 2-nitro-glycals and a series of O-nucleophiles proceeded smoothly in the presence of N-heterocyclic carbene (NHC) catalyst and K₂CO₃ which allowed the highly stereoselective synthesis of the diverse 2-nitro-2,3-unsaturated glycosides in excellent yields. Subsequently, the rearrangement products were conveniently transformed into the desired chiral pyrroles by [3+2] cycloaddition (Barton-Zard reaction) with isocyanoacetate in the presence of Cs₂CO₃. One-pot strategy was also successfully demonstrated for the gram-scale synthesis of one chiral pyrrole. This is the first report of stereoselective conversion from 2-nitroglycals to chiral pyrrole.

Full text of DOI:10.1002/cctc.202100795

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A General Strategy for the Stereoselective Synthesis of
Pyrrole-Fused Chiral Skeletons: [3+2] Cycloaddition with
2-Nitro-2,3-Unsaturated Glycosides
Nan Jiang+,[a] Yuling Mei+,[a] Yu Yang,[a] Youxian Dong,[a] Zekun Ding,[a] and Jianbo Zhang*[a]
In this study, a two-step methodology was developed for the
synthesis of chiral pyrroles from 2-nitroglycals via Ferrier
rearrangement and Barton-Zard reaction under mild conditions
without transition metal catalysts. The Ferrier rearrangement
reaction of 2-nitro-glycals and a series of O-nucleophiles
proceeded smoothly in the presence of N-heterocyclic carbene
(NHC) catalyst and K2CO3 which allowed the highly stereo-
selective synthesis of the diverse 2-nitro-2,3-unsaturated glyco-
sides in excellent yields. Subsequently, the rearrangement
products were conveniently transformed into the desired chiral
pyrroles by [3+2] cycloaddition (Barton-Zard reaction) with
isocyanoacetate in the presence of Cs2CO3. One-pot strategy
was also successfully demonstrated for the gram-scale synthesis
of one chiral pyrrole. This is the first report of stereoselective
conversion from 2-nitroglycals to chiral pyrrole.
Introduction
As a molecular recognition motif, pyrrole is present in many
complex natural products, artificial anion receptors and drugs,
including chlorophyll, porphyrins, antitumor Spiroindimicin B,
Pyrotinib and antiviral Galidesivir (Figure 1).[1] In the pyrrole
family, polysubstituted chiral pyrroles, which constitute an
important family of five-membered N-containing heterocycles
with diverse biological properties and synthetic applications,
have gained increasing attention of the organic and medicinal
chemists.[2] For instance, Phaeosphaeride A and B, which
contain the structural unit of chiral-substituted pyrrole, have
been extensively studied due to their antitumor activity and
ability to inhibit STAT3 signal transduction pathway.[3] As a
result, significant research efforts have been devoted to
achieving the practical, atom- and step-economic synthesis of
chiral pyrrole compounds, with the synthetic methods con-
stantly being innovated and improved.[4]
Figure 1. Bioactive natural products containing a pyrrolic ring.
There are usually two types of strategies for the synthesis of
chiral pyrroles. In the first method, chiral pyrroles are synthe-
sized from achiral raw materials (Scheme 1a). However, this
method is usually limited by the expensive chiral catalysts and
starting materials, along with harsh conditions. The other
method is based on the use of chiral materials, such as
alkaloids, sterols, saccharides, tartaric acid, etc., which can be
easily obtained from nature. Among these, saccharides have
attracted widespread attention and been extensively studied[5]
due to their abundant sources, low cost, mild reaction
conditions and diverse chirality.[6] Therefore, the development
of new synthetic reagents and novel strategies to synthesize
substituted pyrroles from saccharides using mild conditions is
of vital importance.
[a] Dr. N. Jiang,+ Dr. Y. Mei,+ Dr. Y. Yang, Dr. Y. Dong, Dr. Z. Ding,
Prof. J. Zhang
The reactions involving the [3+2] cycloaddition of unsatu-
rated compounds and isocyanoacetate are among the most
effective methods for accessing a pyrrole skeleton.[7] For
instance, Zhao et al. developed a mild cycloaddition reaction of
allenoic acid ester and methyl isocyanoacetate catalyzed by
PPh3 (Scheme 1b).[8] In another study, Zhang et al. reported the
reaction with trifluoromethyl ketene, thereby achieving
trifluoromethyl substituted chiral pyrrolidine derivatives with
high yields and stereoselectivity (Scheme 1c).[9] However, only a
few methods have been developed to date for the synthesis of
School of Chemistry and Molecular Engineering
East China Normal University
Shanghai 200241
E-mail: Jbzhang@chem.ecnu.edu.cn
[+] These authors contribute equally to this manuscript.
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/cctc.202100795
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To the best of our knowledge, this is the first report of NHC-
catalyzed Ferrier rearrangement.
Results and Discussion
In the initial experiments, the screening of
a series of
commercial NHC catalysts was carried out (I–V in Table 1
10 mol%) to ascertain their ability to promote the glycosylation
of tri-O-acetylated 2-nitroglycal 1a with benzyl alcohol 2a. All
NHC catalysts were observed to activate the glycal molecules,
and 3a was obtained in good yields (51–76%), with NHC (I)
exhibiting the optimal result. It implied that the steric bulk in
NHC catalysts plays an important role during the reaction. A
series of bases were also screened for the glycosylation reaction
in the presence of NHC (I). An optimal alkalinity is critical for the
glycosylation reaction. K2CO3 revealed an effective activation of
NHC, while avoiding the decomposition of glycals and products.
Besides, toluene as solvent and room temperature conditions
observed to be suitable. Also, reducing the equivalent of NHC
(I) and K2CO3 to 0.05 is beneficial to the reaction. The donor to
acceptor ratio of 1:2 was employed during the reaction. Finally,
we performed conditional control experiments (Entries 30 and
31). We found that when there was only K2CO3 in the system
without NHC, the corresponding 5a compound was obtained at
a yield of 61% with α:β=3.4:1, indicating that NHC plays an
important role in controlling the stereoselectivity of the product
in this reaction. When NHC (I) was used as catalyst only, the
reaction did not proceed.
After determining the optimal reaction conditions for the
Ferrier rearrangement, the optimal conditions for the [3+2]
cycloaddition with methyl isocyanoacetate 4 and 3a as the
template substrates were explored (Table 2). First, different
bases were screened, and the use of weak bases such as Na2CO3
and K2CO3 did not lead to a smooth reaction. On the other
hand, the use of strong bases such as KOH, NaOH and t-BuOK
promoted the reaction, and 5a was successfully obtained as the
major product in good to excellent yields (68–83%). However,
the formation of by-products was enhanced accordingly due to
high alkalinity. The outcome of the experiment suggested that
3a tended to undergo [3+2] cycloaddition to provide 5a under
the catalytic action of an appropriate base (such as Cs2CO3). The
organic bases such as DBU successfully promoted the reaction,
however, the yield was inferior as compared to Cs2CO3. Using
nucleophilic bases such as DMAP and DABCO, the system
rapidly became complex, and the product 5a was not detected.
The base survey revealed 2 equivalents of Cs2CO3 as the
preferred choice in terms of yield. Subsequently, different
solvents and reaction temperatures were explored. Based on
the earlier optimized conditions, THF as solvent and room
temperature were observed to be suitable. Besides, the donor
to acceptor ratio of 1:1.2 was observed to be optimal.
Scheme 1. Methods of Synthesizing Chiral Pyrrole and This Work.
chiral pyrrole from saccharide skeleton.[1] In 2009, Pathak et al.
reported the synthesis of polysubstituted chiral pyrroles from
vinyl
sulfone-modified
2,3-unsaturated
glycosides
(Scheme 1d).[10] However, due to the harsh reaction conditions,
the substrate scope is limited to only 12 examples. To extend
the reaction generality and applicability, it is envisaged that the
NO2 substitution in the 2,3-unsaturated glycosides would
reduce the electronic density of the double bond, which might
accelerate the process of the proposed [3+2] cycloaddition,
therefore, making the reaction more convenient and amiable,
as a typical Barton-Zard reaction.[11]
In recent years, many efforts have been made for the
synthesis of 2,3-unsaturated glycosides, which are important
precursors for organic synthesis.[12] The Ferrier rearrangement of
glycals is the most common methodology to obtain these
glycosides.[13] However, only a few studies have reported the
synthesis of 2-nitro-2,3-unsaturated glycosides[14] from 2-
nitroglycal.[15] Vankar et al. synthesized 2-nitro-2,3-unsaturated
glycosides by using DMAP as an effective catalyst, and provided
10 substrates. Thus, efforts are still needed to develop a general
methodology that can provide a direct and rapid access to 2-
nitro-2,3-unsaturated glycosides.
In previous studies, the substituent, sugar type and reaction
conditions have been observed to have a significant influence
on the reaction with glycals, even with the same catalyst.[16–19]
Chen et al. recently reported an efficient stereoselective
addition of perbenzylated 2-nitrogalactals with alcohols cata-
lyzed by N-heterocyclic carbene (NHC).[20] In order to achieve
the Ferrier rearrangement of 2-nitroglycal, we envisage that the
introduction of acetyl substitution in glycals would accelerate
the proposed Ferrier rearrangement. Thus, based on NHC
catalysis, an efficient method for the synthesis of 2-nitro-2,3-
unsaturated glycoside from 2-nitroglycals has been developed.
After determining the reaction conditions, the substrate
scope for the glycosylation reaction with different nucleophiles
was subsequently explored. As shown in Table 3, for benzyl
alcohol or benzyl alcohol containing substituents, the reaction
proceeded smoothly, and the products 3a–3d were obtained
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Table 1. Optimization of the Ferrier rearrangement reaction conditions.[a]
Table 2. Optimization of the [3+2] cycloaddition reaction conditions.[a]
[a] The reaction was conducted with 3 (0.1 mmol, 1 equiv.), using 1 mL
solvent; [b] Isolated yield; [c] n.d.=not detected.
with excellent yields. The simple alcohols (2e–2h) were suitable
for the reaction, and the rearrangement products were
obtained with yields of 81–84%. Notably, the substrates bearing
halogen functionalities 3e–3f underwent the desired trans-
formation without any elimination side reactions, thus, offering
opportunities for further synthetic transformations. For fluorene
methanol 2k, the corresponding rearrangement product 3k
was obtained with excellent yield. Besides, the reaction
tolerated alcohols containing double or triple bonds, such as
propargyl alcohol and allyl alcohol, with the corresponding
products 3l–3m obtained in high yields. Reducing the temper-
ature was beneficial to enhance the yield of 3n. The hetero-
aromatic compound was compatible with the transformation
process, thus, affording the desired 3o in 79% yield. Moreover,
the glycosyl acceptor 2p also was applied to the system, and
the corresponding disaccharide 3p was obtained. The reaction
was also noted to be applicable to cholesterol with complex
structure. For a few secondary alcohols, such as isopropanol
and cyclohexanol, the yields of 3r and 3s were observed to
decline. The reaction proceeded smoothly for galactose donors
3t–3u. Subsequently, 3a–3u were successfully converted to
[a] The reaction was conducted with 1a (0.2 mmol, 1 equiv.). using 2 mL
solvent; [b] Isolated yield; [c] n.d.=not determined.
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Table 3. Scope of substrate.[a,b,c]
selectivity of 3a–3u and 5a–5u were confirmed by NMR
spectroscopy to be very high (α:β>30:1).[14b] However, using
tert-butanol as a nucleophile, the rearrangement product was
not detected, probably due to its steric hinderance. Phenol was
successfully converted into the corresponding 2-nitro-2,3-unsa-
turated phenolic glycoside with 0.15 equivalent of K2CO3.
Nevertheless, the corresponding 2, 3-unsaturated glycoside
decomposed rapidly under the Barton-Zard conditions. The
attempts to prepare S-glycosides using benzyl mercaptan were
not successful, with almost no formation of the rearrangement
products.
After evaluating the universality of the substrate, the
practical synthesis of chiral pyrrole via “one-pot” strategy was
investigated.[18,21] First, gram-scale 1a and 2a underwent the
Ferrier rearrangement reaction, as shown in Scheme 2. After the
completion of the reaction, 4 and Cs2CO3 were added into the
reaction mixture, and the desired product 5a was obtained
with a total yield of 74%. For the first time, the conversion from
nitroglycal to chiral pyrrole was successfully realized in one pot.
As compared with the total yield of 82% in two step process,
the one-pot strategy was comparable, which also afforded the
use of affordable toluene. The gram-scale one-pot synthesis
fully illustrated the applicability of the proposed novel method
for the synthesis of chiral pyrrole.
The Ferrier rearrangement of glycals is usually known to
generate the α:β anomeric mixtures of products in acidic
conditions.[12b] However, in this study, the Ferrier rearrangement
of nitroglycal formed the sole α anomers in the basic
conditions, which were not altered during the subsequent
Barton-Zard reactions. In order to explore the mechanism of the
reaction, a series of glycal donors was further investigated. As
previously shown, acetylated galactal reacted smoothly in the
presence of NHC, thus, forming 5t–5u. However, no Ferrier
rearrangement products were detected once the protective
group on the sugar ring was replaced with the benzyl group,
which is a poor leaving group for the conditions in this study.[22]
The same phenomenon took place on substituting the nitro
group at the C-2 position by Cl or H, which indicated that both
acetyl group and nitro substitution on the sugar ring were
essential in the rearrangement step.
Based on the obtained findings and literature studies, a
reaction mechanism may be proposed as follows
(Scheme 3).[11,13,20] Firstly, NHC (I) is deprotonated in the
presence of potassium carbonate to generate carbene A, which
interacts with the hydroxyl group of the nucleophiles through
hydrogen bonding to generate NHC-HOR complex B. After-
[a] The reaction was conducted with 1 equiv. (0.2 mmol) of 1a and
2 equiv. (0.4 mmol) of 2a. The [3+2] cycloaddition reaction was
conducted with 1 equiv. (0.1 mmol) of 3a and 1.2 equiv. (1.2 mmol) of 4;
1
[b] Isolated yield; [c] Diastereoselective (α:β) ratio determined by H NMR
°
analysis; [d] The reaction was conducted at 0 C.
the desired [3+2] cycloaddition products 5a–5u with high
yields (up to 99%). Moreover, ethyl isocyanoacetate was proven
as an effective substrate in Barton-Zard reaction to give another
[3+2] cycloaddition product 5v. The structure and stereo-
chemistry of the rearrangement and cycloaddition products
were elucidated by NMR and mass spectroscopy and were
subsequently compared with the reported data.[14] The stereo-
Scheme 2. One-pot Synthesis of Chiral Pyrrole 5a by gram scale-up reaction.
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Experimental Section
General information: All reactions were carried out under dry
nitrogen atmosphere. All solvents and reagents were obtained from
commercial sources unless otherwise stated and were purified
according to standard procedures. All NHC catalysts were pur-
chased from the Energy Chemical Inc. (China). Removal of solvent
in vacuo refers to distillation using a rotary evaporator attached to
an efficient vacuum pump. 1H NMR and 13C NMR spectra were
recorded on Bruker DRX-500 NMR spectrometer in solutions of
CDCl3 using tetramethylsilane as the internal standard. Mass spectra
were determined on LTQ-XL (Thermo scientific, USA) with an (ESI)
Ion trap mass spectrometer. Optical rotations were measured using
°
a polarimeter at 25 C.
General procedure for the synthesis of 2-nitroglycal:[14b] To a
stirred solution of a glycal (1 mmol) and AgNO3 (1 mmol) in
°
acetonitrile (10.0 mL) at 0 C was added dropwise acetyl chloride
(1 mmol). After the completion of the addition, the reaction was
°
stirred at 55 C monitored by TLC (PE/EA, 2:1) until the glycal donor
was consumed completely. The reaction mixture was brought to
room temperature and was neutralized to pH 7 by the addition of
solid NaHCO3. The suspension was filtered and concentrated. The
solvent was removed under reduced pressure to afford a crude
product which was purified by silica gel flash chromatography with
a gradient solvent system (PE/EA, 4:1) to yield 2-nitroglycals.
Scheme 3. Proposed Mechanism.
General procedure for the synthesis of 2-nitro-2,3-unsaturated
glycosides: To a mixture of 2-nitroglycal (63.4 mg, 0.2 mmol),
alcohol acceptor (0.4 mmol), NHC (I) (4.3 mg, 0.01 mmol) and K2CO3
(1.4 mg, 0.01 mmol) were added toluene (2.0 mL) under an
atmosphere of nitrogen. The reaction mixture was stirred at room
temperature and monitored by TLC (PE/EA, 2:1) until the glycal
donor was consumed completely. The solvent was removed under
reduced pressure to afford a crude product which was purified by
silica gel flash chromatography with a gradient solvent system (PE/
EA, 4:1) to yield 2-nitro-2, 3-unsaturated glycosides.
wards, complex B and nitro group of nitroglycal 1a form
complex C through hydrogen bonding. Subsequently, the
alkoxy group in complex C undergoes nucleophilic addition
from the α surface of the sugar ring which has less steric
hindrance to the anomeric center, and at the same time the
protons in the alcohol are transferred to the nitro group to
form a stable carbanion D. Simultaneously, the organic catalyst
A is regenerated. Finally, complex D undergoes an elimination
to get rid of acetic acid, thereby producing 2-nitro-2,3-
unsaturated glycoside 3. Further, 3 undergoes a classic Barton-
Zard reaction process to form the final pyrrole product 5.
General procedure for the synthesis of chiral pyrroles: To a
mixture of 2-nitro-2,3-unsaturated glycoside (0.1 mmol), methyl
isocyanoacetate (12.0 mg, 0.12 mmol) and Cs2CO3 (65.2 mg,
0.2 mmol) were reacted in THF under an atmosphere of nitrogen.
The reaction mixture was stirred at room temperature and
monitored by TLC (PE/EA, 2:1) until the 2-nitro-2,3-unsaturated
glycoside was consumed completely. The solvent was removed
under reduced pressure to afford a crude product which was
purified by silica gel flash chromatography with a gradient solvent
system (PE/EA, 2:1) to yield chiral pyrroles.
Conclusion
In summary, a general strategy has been successfully developed
for the synthesis of structurally diverse chiral pyrrole molecules
without using the transition metal catalysts. In this context, the
NHC-catalyzed Ferrier rearrangement was first successfully
achieved with acetylated nitroglycals and a series of O-
nucleophiles in basic conditions. The as-developed 2-nitro-2,3-
unsaturated glycosides were subsequently applied as an alkyne
equivalent during the [3+2] N-heterocyclic addition to form
pyrrole-fused skeletons in mild conditions. By employing this
novel strategy, βsubstituted chiral pyrroles were effectively
synthesized with excellent yields and high stereoselectivity. To
further demonstrate the practicability of the proposed method-
ology, the gram-scale Ferrier rearrangement of 2-nitroglycals
and Barton-Zard reaction were successfully demonstrated in
one pot. Overall, the innovative transformation reported in this
study is expected to find widespread applications in the
synthesis of pyrrole-containing natural products and drugs.
((2R,3S,6S)-3-acetoxy-6-(benzyloxy)-5-nitro-3,6-dihydro-2H-pyran-
2-yl)methyl acetate (3a):[14b] Colorless syrup. 1H NMR (500 MHz,
CDCl3) δ 7.38–7.32 (m, 5H), 7.20 (d, J=2.2 Hz, 1H), 5.71 (s, 1H), 5.59
(dd, J=9.3, 1.7 Hz, 1H), 4.84 (d, J=11.2 Hz, 1H), 4.76 (d, J=11.2 Hz,
1H), 4.30–4.23 (m, 2H), 4.18 (t, J=7.4 Hz, 1H), 2.13 (s, 3H), 2.11 (s,
3H). 13C NMR (126 MHz, CDCl3) δ 170.6, 169.8, 148.1, 136.4, 132.9,
128.6, 128.4, 128.4, 92.0, 71.9, 66.6, 64.5, 62.0, 20.8, 20.7. HRMS (ESI):
m/z Calcd for C17H19NNaO8 [M+Na]+: 388.1003, found 388.1013.
((2R,3S,6S)-3-acetoxy-6-((4-methoxybenzyl)oxy)-5-nitro-3,6-dihy-
dro-2H-pyran-2-yl)methyl acetate (3b):[14b] Colorless syrup. 1H NMR
(500 MHz, CDCl3) δ 7.29 (d, J=8.5 Hz, 2H), 7.18 (d, J=2.1 Hz, 1H),
6.89 (d, J=8.5 Hz, 2H), 5.67 (s, 1H), 5.57 (dd, J=9.7, 1.3 Hz, 1H)„ 4.78
(d, J=10.9 Hz, 1H), 4.67 (d, J=10.9 Hz, 1H), 4.34–4.17 (m, 3H), 3.80
(s, 3H), 2.12 (s, 3H), 2.12 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.6,
169.8, 159.8, 148.2, 132.8, 130.1, 128.4, 114.0, 91.6, 71.5, 66.47, 64.5,
62.0, 55.3, 20.8, 20.7. HRMS (ESI): m/z Calcd for C18H21NNaO9 [M+
Na]+: 418.1109, found 418.1111.
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((2R,3S,6S)-3-acetoxy-6-((4-chlorobenzyl)oxy)-5-nitro-3,6-dihydro-
2H-pyran-2-yl) methyl acetate (3c): Colorless syrup. [α]25 D= +
13.2 (c 0.83, CH2Cl2). IR (neat) vmax 2920, 1742, 1532, 1372, 1215,
1105, 1018, 732 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ 7.35–7.28 (m, 4H),
7.21 (d, J=2.2 Hz, 1H), 5.67 (s, 1H), 5.61–5.55 (dd, 1H), 4.81 (d, J=
11.5 Hz, 1H), 4.71 (d, J=11.5 Hz, 1H), 4.28–4.20 (m, 3H), 2.14 (s, 3H),
2.11 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.6, 169.8, 147.9, 134.9,
134.3, 133.1, 129.7, 128.8, 91.9, 71.0, 66.7, 64.5, 62.0, 20.8, 20.8.
HRMS (ESI): m/z Calcd for C17H18ClNNaO9 [M+Na]+: 422.0613, found
422.0611.
(s, 1H), 5.59–5.55 (m, 1H), 4.34 (ddd, J=9.7, 4.8, 2.5 Hz, 1H), 4.30–
4.24 (m, 2H), 4.09 (t, J=5.9 Hz, 2H), 3.57–3.49 (m, 2H), 2.15 (s, 3H),
2.10 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.6, 169.8, 147.6, 133.2,
92.4, 70.0, 66.9, 64.3, 61.9, 30.0, 20.8, 20.8. HRMS (ESI): m/z Calcd for
C12H16BrNNaO8 [M+Na]+: 403.9951, found 403.9952.
((2R,3S,6S)-3-acetoxy-5-nitro-6-(2,2,2-tribromoethoxy)-3,6-dihy-
dro-2H-pyran-2-yl)methyl acetate (3j): Colorless syrup. [α]25 D=
+106.1 (c 0.49, CH2Cl2). IR (neat) vmax 2962, 1738, 1532, 1370, 1208,
1084, 1019, 630 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ 7.31 (d, J=2.1 Hz,
1H), 5.83 (s, 1H), 5.63 (dd, J=9.9, 1.3 Hz, 1H), 4.59 (d, J=10.9 Hz,
1H), 4.53 (d, J=10.9 Hz, 1H), 4.46 (ddd, J=10.2, 4.8, 2.4 Hz, 1H), 4.32
(dd, J=12.4, 2.4 Hz, 1H), 4.27 (dd, J=12.4, 5.0 Hz, 1H), 2.17 (s, 3H),
2.11 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.6, 169.8, 146.9, 134.0,
91.7, 83.4, 67.5, 64.3, 61.8, 36.4, 20.8, 20.8. HRMS (ESI): m/z Calcd for
C12H14Br3NNaO8 [M+Na]+: 559.8162, found 559.8168.
((2R,3S,6S)-3-acetoxy-6-((2-iodobenzyl)oxy)-5-nitro-3,6-dihydro-
2H-pyran-2-yl)methyl acetate (3d): Colorless syrup. [α]25 D= +
78.8 (c 0.21, CH2Cl2). IR (neat) vmax 2921, 1735, 1529, 1370, 1211,
1104, 1013, 600 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ 7.84 (d, J=7.9 Hz,
1H), 7.43 (d, J=7.5 Hz, 1H), 7.36 (t, J=7.5 Hz, 1H), 7.23 (d, J=2.0 Hz,
1H), 7.02 (t, J=7.6 Hz, 1H), 5.75 (s, 1H), 5.63–5.58 (m, 1H), 4.92 (d,
J=11.9 Hz, 1H), 4.74 (d, J=12.0 Hz, 1H), 4.35 (ddd, J=9.6, 4.7,
2.4 Hz, 1H), 4.28 (dd, J=12.3, 4.9 Hz, 1H), 4.22 (dd, J=12.3, 2.2 Hz,
1H), 2.14 (s, 3H), 2.11 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.6,
169.8, 147.9, 139.4, 138.9, 133.1, 129.9, 129.7, 128.5, 98.3, 92.0, 75.5,
66.8, 64.4, 62.0, 20.9, 20.8. HRMS (ESI): m/z Calcd for C17H18INNaO9
[M+Na]+: 513.9969, found 513.9977.
(2R,3S,6S)-6-((9H-fluoren-9-yl)methoxy)-2-(acetoxymethyl)-5-
nitro-3,6-dihydro-2H-pyran-3-yl acetate (3k): Colorless syrup. [α]
25 D= +145.3 (c 2.12, CH2Cl2). IR (neat) vmax 3068, 1742, 1532, 1370,
1216, 1104, 1019 cmÀ 1 1H NMR (500 MHz, CDCl3) δ 7.77 (d, J=
.
7.6 Hz, 2H), 7.57 (dd, J=13.4, 7.5 Hz, 2H), 7.40 (td, J=7.4, 2.2 Hz,
2H), 7.31 (dt, J=16.1, 7.5 Hz, 2H), 7.25 (d, J=1.9 Hz, 1H), 5.68 (s,
1H), 5.59–5.54 (m, 1H), 4.23–4.15 (m, 4H), 4.06 (dd, J=7.0, 2.7 Hz,
2H), 2.18 (s, 3H), 1.95 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.5,
169.8, 148.0, 144.4, 144.0, 141.3, 133.0, 127.8, 127.8, 127.2, 127.1,
125.2, 125.0, 120.1, 120.0, 92.6, 77.3, 72.4, 66.8, 64.5, 61.9, 47.6, 20.8,
20.6. HRMS (ESI): m/z Calcd for C24H23NNaO9 [M+Na]+: 476.1316,
found 476.1323.
((2R,3S,6S)-3-acetoxy-6-methoxy-5-nitro-3,6-dihydro-2H-pyran-2-
yl)methyl acetate (3e):[14b] Colorless syrup. 1H NMR (500 MHz,
CDCl3) 1H NMR (500 MHz, CDCl3) δ 7.18 (d, J=2.2 Hz, 1H), 5.57 (dd,
J=9.7, 1.4 Hz, 1H), 5.47 (s, 1H), 4.26 (t, J=3.4 Hz, 2H), 4.21 (ddd, J=
9.5, 4.6, 2.8 Hz, 1H), 3.55 (s, 3H), 2.14 (s, 3H), 2.10 (s,3H). 13C NMR
(126 MHz, CDCl3) δ 170.6, 169.8, 148.1, 132. 7, 93.4, 66.3, 64.4, 62.0,
57.0, 20.7. HRMS (ESI): m/z Calcd for C11H15NNaO8 [M+Na]+:
312.0690, found 312.0694.
((2R,3S,6S)-3-acetoxy-5-nitro-6-(prop-2-yn-1-yloxy)-3,6-dihydro-
2H-pyran-2-yl)methyl acetate (3l): Colorless syrup. [α]25 D= +
195.3 (c 1.22, CH2Cl2). IR (neat) vmax 2927, 1738, 1532, 1370, 1214,
1
((2R,3S,6S)-3-acetoxy-6-ethoxy-5-nitro-3,6-dihydro-2H-pyran-2-yl)
methyl acetate (3f): Colorless syrup. [α]25 D= +144.2 (c 2.84,
CH2Cl2). IR (neat) vmax 2923, 1742, 1535, 1369, 1215, 1111,
1022 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ 7.16 (d, J=2.0 Hz, 1H), 5.60–
5.53 (m, 2H), 4.29–4.22 (m, 3H), 3.93–3.85 (m, 1H), 3.79–3.71 (m, 1H),
2.14 (s, 3H), 2.10 (s, 3H), 1.26 (t, J=7.1 Hz, 3H). 13C NMR (126 MHz,
CDCl3) δ 170.7, 169.9, 148.4, 132.5, 92.2, 66.4, 65.8, 64.5, 62.1, 20.8,
15.1. HRMS (ESI): m/z Calcd for C12H17NNaO8 [M+Na]+: 326.0846,
found 326.0849.
1016, 659 cmÀ 1. H NMR (500 MHz, CDCl3) δ 7.22 (d, J=2.2 Hz, 1H),
5.78 (s, 1H), 5.60 (dd, J=9.0, 1.9 Hz, 1H), 4.42 (dd, J=15.6, 2.4 Hz,
1H), 4.38 (dd, J=15.6, 2.4 Hz, 1H), 4.29–4.24 (m, 3H), 2.54 (t, J=
2.4 Hz, 1H), 2.14 (s, 3H), 2.10 (s, 3H). 13C NMR (126 MHz, CDCl3) δ
170.50, 169.68, 147.60, 133.17, 91.03, 77.86, 75.70, 66.63, 64.25,
61.71, 56.37, 20.67, 20.65.
((2R,3S,6S)-3-acetoxy-6-(allyloxy)-5-nitro-3,6-dihydro-2H-pyran-2-
yl)methyl acetate (3m):[14b] Colorless syrup. 1H NMR (500 MHz,
CDCl3) δ 7.19 (d, J=2.2 Hz, 1H), 6.01–5.90 (m, 1H), 5.63 (s, 1H), 5.61–
5.55 (m, 1H), 5.34 (dd, J=17.2, 1.5 Hz, 1H), 5.26 (dd, J=10.4, 1.2 Hz,
1H), 4.32 (dd, J=12.5, 5.5 Hz, 1H), 4.29–4.20 (m, 4H), 2.15 (s, 3H),
2.11 (s, 3H).
((2R,3S,6S)-3-acetoxy-6-isobutoxy-5-nitro-3,6-dihydro-2H-pyran-
2-yl)methyl acetate (3g): Colorless syrup. [α]25 D= +80.6 (c 2.00,
CH2Cl2). IR (neat) vmax 2962, 1738, 1532, 1364, 1214, 1107,
1016 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ 7.16 (d, J=2.2 Hz, 1H), 5.57–
5.52 (m, 2H), 4.26–4.21 (m, 3H), 3.58 (dd, J=9.1, 6.8 Hz, 1H), 3.46
(dd, J=9.1, 6.4 Hz, 1H), 2.14 (s, 3H), 2.09 (s, 3H), 1.90 (dt, J=13.3,
6.7 Hz, 1H), 0.91 (dd, J=6.7, 2.7 Hz, 6H). 13C NMR (126 MHz, CDCl3)
δ 170.6, 169.8, 148.3, 132.5, 92.5, 77.0, 66.4, 64.51, 62.1, 28.4, 20.8,
19.3, 19.2. HRMS (ESI): m/z Calcd for C14H21NNaO8 [M+Na]+:
354.1159, found 354.1153.
((2R,3S,6S)-3-acetoxy-6-(cinnamyloxy)-5-nitro-3,6-dihydro-2H-
pyran-2-yl)methyl acetate (3n): Colorless syrup. [α]25 D= +33.7 (c
1.93, CH2Cl2). IR (neat) vmax 3024, 1741, 1535, 1370, 1216, 1087,
1
1007 cmÀ 1. H NMR (500 MHz, CDCl3) δ 7.41 (d, J=7.3 Hz, 2H), 7.33
(t, J=7.5 Hz, 2H), 7.26 (d, J=1.9 Hz, 1H), 7.21 (d, J=2.2 Hz, 1H), 6.66
(d, J=15.9 Hz, 1H), 6.35–6.28 (m, 1H), 5.71 (s, 1H), 5.60 (dd, J=9.3,
1.4 Hz, 1H), 4.49 (ddd, J=12.3, 5.9, 1.3 Hz, 1H), 4.42–4.38 (m, 1H),
4.30 (dt, J=8.8, 3.4 Hz, 3H), 2.15 (s, 3H), 2.11 (s, 3H). 13C NMR
(126 MHz, CDCl3) δ 170.6, 169.8, 148.3, 136.3, 134.3, 132.8, 128.7,
128.2, 126.7, 124.1, 91.3, 70.2, 66.5, 64.5, 62.1, 20.8, 20.8. HRMS (ESI):
m/z Calcd for C19H21NNaO8 [M+Na]+: 414.1159, found 414.1156.
((2R,3S,6S)-3-acetoxy-6-(hexyloxy)-5-nitro-3,6-dihydro-2H-pyran-
2-yl)methyl acetate (3h): Colorless syrup. [α]25 D= +75.2 (c 3.20,
CH2Cl2). IR (neat) vmax 2926, 1742, 1538, 1366, 1218, 1111,
1
1022 cmÀ 1. H NMR (500 MHz, CDCl3) δ 7.16 (d, J=2.1 Hz, 1H), 5.55
(d, J=5.2 Hz, 2H), 4.27–4.20 (m, 3H), 3.84–3.77 (m, 1H), 3.67 (dt, J=
9.4, 6.5 Hz, 1H), 2.13 (s, 3H), 2.09 (s, 3H), 1.60 (dd, J=13.9, 6.9 Hz,
2H), 1.30 (dd, J=20.9, 6.2 Hz, 6H), 0.87 (t, J=6.6 Hz, 3H).). 13C NMR
(126 MHz, CDCl3) δ 170.6, 169.8, 148.3, 132.4, 92.4, 70.4, 66.4, 64.5,
62.1, 31.5, 29.4, 25.7, 22.6, 20.8, 14.1. HRMS (ESI): m/z Calcd for
C16H25NNaO8 [M+Na]+: 382.1472, found 382.1468.
((2R,3S,6S)-3-acetoxy-6-(furan-2-ylmethoxy)-5-nitro-3,6-dihydro-
2H-pyran-2-yl)methyl acetate (3o) Colorless syrup. [α]25 D= +
83.4 (c 2.01, CH2Cl2). IR (neat) vmax 2921, 1741, 1532, 1370, 1216,
1107, 1013 cmÀ 1 1H NMR (600 MHz, CDCl3) δ 7.52 (dd, J=1.9,
.
0.8 Hz, 1H), 7.26 (d, J=2.3 Hz, 1H), 6.48 (d, J=3.2 Hz, 1H), 6.45 (dd,
J=3.3, 1.9 Hz, 1H), 5.77 (s, 1H), 5.69–5.65 (m, 1H), 4.81 (q, J=
12.7 Hz, 2H), 4.37–4.31 (m, 2H), 4.30–4.25 (m, 1H), 2.21 (s, 3H), 2.19
(s, 3H). 13C NMR (151 MHz, CDCl3) δ 170.57, 169.74, 150.07, 147.88,
143.39, 132.88, 110.53, 110.44, 91.34, 66.46, 64.28, 63.04, 61.81,
((2R,3S,6S)-3-acetoxy-6-(2-bromoethoxy)-5-nitro-3,6-dihydro-2H-
pyran-2-yl)methyl acetate (3i): Colorless syrup. [α]25 D= +49.6 (c
0.31, CH2Cl2). IR (neat) vmax 2956, 1738, 1529, 1349, 1217, 1107,
1
1022 cmÀ 1. H NMR (500 MHz, CDCl3) δ 7.21 (d, J=2.1 Hz, 1H), 5.61
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20.71, 20.67. HRMS (ESI): m/z Calcd for C15H17NNaO9 [M+Na]+:
378.0796, found 378.0804.
(500 MHz, CDCl3) δ 9.49 (s, 1H), 7.40–7.33 (m, 4H), 7.29 (t, J=7.1 Hz,
1H), 6.87 (d, J=3.0 Hz, 1H), 6.27 (d, J=8.9 Hz, 1H), 5.77 (s, 1H), 4.84
(t, J=10.2 Hz, 1H), 4.71–4.67 (m, 1H), 4.25 (ddd, J=24.0, 14.7,
7.6 Hz, 3H), 3.78 (s, 3H), 2.10 (s, 3H), 2.08 (s, 3H). 13C NMR (126 MHz,
CDCl3) δ 170.9, 170.5, 160.6, 137.6, 128.6, 128.1, 127.9, 123.2, 121.8,
118.8, 118.6, 93.4, 69.7, 68.6, 63.1, 51.8, 20.9, 20.9. HRMS (ESI): m/z
Calcd for C21H23NNaO8 [M+Na]+: 440.1316, found 440.1311.
((2R,3S,6S)-3-acetoxy-5-nitro-6-(((3aR,5R,5aS,8aS,8bR)-2,2,7,7-
tetramethyltetrahydro-5H-bis([1,3]dioxolo)[4,5-b:4’,5’-d]pyran-5-
yl)methoxy)-3,6-dihydro-2H-pyran-2-yl)methyl acetate (3p): Col-
orless syrup. [α]25 D= +21.3 (c 2.15, CH2Cl2). IR (neat) vmax 2986,
1
1744, 1540, 1367, 1211, 1066, 1001 cmÀ 1. H NMR (500 MHz, CDCl3)
δ 7.19 (d, J=2.2 Hz, 1H), 5.62 (s, 1H), 5.60–5.55 (m, 1H), 5.51 (d, J=
5.0 Hz, 1H), 4.60 (dd, J=7.9, 2.3 Hz, 1H), 4.32–4.27 (m, 3H), 4.26–
4.20 (m, 2H), 3.99–3.86 (m, 3H), 2.14 (s, 3H), 2.10 (s, 3H), 1.51 (s, 3H),
1.44 (s, 3H), 1.34 (s, 3H), 1.32 (s, 3H). 13C NMR (126 MHz, CDCl3) δ
170.7, 169.9, 148.0, 133.1, 109.4, 108.7, 96.4, 92.8, 71.0, 70.7, 70.6,
69.0, 66.8, 66.4, 64.4, 62.0, 26.1, 26.0, 25.0, 24.4, 20.8, 20.8. HRMS
(ESI): m/z Calcd for C22H31NNaO13 [M+Na]+: 540.1688, found
540.1681.
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-((4-meth-
oxybenzyl)oxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxy-
late (5b): Colorless syrup. [α]25 D=À 30.3 (c 2.05, CH2Cl2). IR (neat)
vmax 3307, 3030, 2953, 1735, 1612, 1233, 1153, 1012, 729 cmÀ 1. H
1
NMR (500 MHz, CDCl3) δ 9.29 (s, 1H), 7.31 (d, J=8.5 Hz, 2H), 6.89 (d,
J=8.5 Hz, 2H), 6.85 (d, J=3.1 Hz, 1H), 6.27 (d, J=8.6 Hz, 1H), 5.75 (s,
1H), 4.78 (d, J=11.4 Hz, 1H), 4.62 (d, J=11.4 Hz, 1H), 4.33–4.22 (m,
3H), 3.80 (s, 3H), 3.78 (s, 3H), 2.12 (s, 3H), 2.08 (s, 3H). 13C NMR
(126 MHz, CDCl3) δ 170.9, 170.5, 160.5, 159.5, 129.8, 129.7, 123.3,
122.0, 118.8, 118.4, 114.0, 93.1, 77.4, 77.1, 76.9, 69.4, 68.5, 63.2, 63.1,
55.4, 51.8, 21.0, 21.0. HRMS (ESI): m/z Calcd for C22H25NNaO9 [M+
Na]+: 470.1422, found 470.1430.
((2R,3S,6S)-3-acetoxy-6-(((3S,8S,9S,10R,13R,14S,17R)-10,13-
dimethyl-17-((R)-6-methylheptan-2-yl)-
2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta
[a]phenanthren-3-yl)oxy)-5-nitro-3,6-dihydro-2H-pyran-2-yl)
methyl acetate (3q): White solid. [α]25 D= +138.4 (c 0.41, CH2Cl2).
Methyl (4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-((4-chloroben-
zyl)oxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate
(5c): Colorless syrup. [α]25 D=À 27.1 (c 1.22, CH2Cl2). IR (neat) vmax
IR (neat) vmax 2933, 1732, 1532, 1367, 1228, 1101, 1025 cmÀ 1 1H
.
NMR (500 MHz, CDCl3) δ 7.16 (d, J=2.2 Hz, 1H), 5.71 (s, 1H), 5.54
(dd, J=9.7, 1.6 Hz, 1H), 5.37 (d, J=5.2 Hz, 1H), 4.35–4.30 (m, 1H),
4.26 (dd, J=9.6, 7.3 Hz, 2H), 3.65 (ddd, J=16.2, 11.1, 4.8 Hz, 1H),
2.42–2.33 (m, 2H), 2.15 (s, 3H), 2.10 (s, 3H), 2.05–1.95 (m, 41H). 13C
NMR (126 MHz, CDCl3) δ 170.7, 169.9, 148.7, 140.5, 132.3, 122.4,
91.1, 80.3, 66.4, 64.7, 62.3, 56.8, 56.2, 50.2, 42.4, 40.3, 39.8, 39.6, 37.1,
36.8, 36.3, 35.9, 32.0, 32.0, 28.3, 28.1, 27.9, 24.4, 23.9, 22.9, 22.7, 21.1,
20.8, 20.8, 19.4, 18.8, 12.0. HRMS (ESI): m/z Calcd for C37H57NNaO8
[M+Na]+: 666.3976, found 666.3987.
3301, 3030, 2950, 1735, 1581, 1230, 1156, 1006, 803, 769 cmÀ 1. H
1
NMR (500 MHz, CDCl3) δ 9.34 (d, J=22.0 Hz, 1H), 7.32 (s, 4H), 6.87
(d, J=3.0 Hz, 1H), 6.27 (d, J=8.7 Hz, 1H), 5.75 (s, 1H), 4.82 (d, J=
12.0 Hz, 1H), 4.65 (d, J=12.0 Hz, 1H), 4.32–4.21 (m, 3H), 3.79 (s, 3H),
2.10 (s, 3H), 2.09 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.9, 170.5,
160.5, 136.1, 133.7, 129.4, 128.8, 123.2, 121.6, 118.9, 118.5, 93.4,
68.9, 68.7, 63.1, 63.1, 51.9, 21.0, 21.0. HRMS (ESI): m/z Calcd for
C21H22ClNNaO8 [M+Na]+: 474.0926, found 474.0936.
((2R,3S,6S)-3-acetoxy-6-isopropoxy-5-nitro-3,6-dihydro-2H-pyran-
2-yl)methyl acetate (3r):[14a] Colorless syrup. 1H NMR (500 MHz,
CDCl3) δ 7.15 (d, J=2.2 Hz, 1H), 5.66 (s, 1H), 5.55 (dd, J=9.3, 1.8 Hz,
1H), 4.31–4.27 (m, 1H), 4.27–4.23 (m, 2H), 4.07 (m, J=6.2 Hz, 1H),
2.14 (s, 3H), 2.10 (s, 3H), 1.25 (dd, J=14.6, 6.2 Hz, 6H). 13C NMR
(126 MHz, CDCl3) δ170.6, 169.8, 148.6, 132.2, 91.2, 73.2, 66.2, 64.6,
62.2, 23.3, 21.7, 20.7, 20.7. HRMS (ESI): m/z Calcd for C13H19NNaO8
[M+Na]+: 340.1003, found 340.1007.
Methyl (4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-((2-iodobenzyl)
oxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate (5d):
Colorless syrup. [α]25 D=À 7.4 (c 1.96, CH2Cl2). IR (neat) vmax 3301,
1
3052, 2950, 1732, 1584, 1440, 1227, 1006, 735, 566 cmÀ 1. H NMR
(500 MHz, CDCl3) δ 9.34 (s, 1H), 7.84 (dd, J=7.9, 0.9 Hz, 1H), 7.45
(dd, J=7.6, 1.4 Hz, 1H), 7.34 (td, J=7.5, 0.9 Hz, 1H), 7.00 (td, J=7.7,
1.6 Hz, 1H), 6.96 (d, J=3.1 Hz, 1H), 6.29 (d, J=8.6 Hz, 1H), 5.85 (s,
1H), 4.85 (d, J=12.5 Hz, 1H), 4.67 (d, J=12.5 Hz, 1H), 4.29 (ddd, J=
19.4, 11.4, 7.6 Hz, 3H), 3.79 (s, 3H), 2.11 (s, 3H), 2.09 (s, 3H). 13C NMR
(126 MHz, CDCl3) δ 170.9, 170.5, 160.5, 140.0, 139.4, 129.6, 129.4,
128.4, 123.3, 121.7, 118.9, 118.6, 98.3, 94.1, 73.8, 68.9, 63.2, 63.1,
51.9, 21.0, 21.0. HRMS (ESI): m/z Calcd for C21H22INNaO8 [M+Na]+:
566.0282, found 566.0275.
((2R,3S,6S)-3-acetoxy-6-(cyclohexyloxy)-5-nitro-3,6-dihydro-2H-
pyran-2-yl)methyl acetate (3s):[14b] Colorless syrup. 1H NMR
(500 MHz, CDCl3) 1H NMR (500 MHz, CDCl3) δ 7.15 (d, J=2.2 Hz, 1H),
5.70 (s, 1H), 5.55 (ddd, J=9.7, 2.2, 0.8 Hz, 1H), 4.32–4.28 (m, 1H),
4.27–4.23 (m, 2H), 3.77 (td, J=9.0, 4.5 Hz, 1H), 2.14 (s, 3H), 2.09 (s,
3H), 1.92 (s, 2H), 1.74–1.70 (m, 2H), 1.43–1.23 (m, 6H). 13C NMR
(126 MHz, CDCl3) δ 170.6, 169.9, 148.7, 132.2, 91.2, 78.7, 66.3, 64.7,
62.3, 33.5, 31.6, 25.5, 24.0, 23.8, 20.8, 20.8. HRMS (ESI): m/z Calcd for
C16H23NNaO8 [M+Na]+: 380.1316, found 380.1319.
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-methoxy-
2,4,6,7-tetrahydro-pyrano[3,4-c]pyrrole-1-carboxylate (5e): Color-
less syrup. [α]25 D=À 11.4 (c 1.33, CH2Cl2). IR (neat) vmax 3298, 3040,
2953, 1704, 1440, 1372, 1332, 1230, 1018, 735 cmÀ 1 1H NMR
.
(500 MHz, CDCl3) δ 9.31 (s, 1H), 6.90 (d, J=3.1 Hz, 1H), 6.26 (d, J=
9.2 Hz, 1H), 5.58 (s, 1H), 4.29 (d, J=4.6 Hz, 2H), 4.20–4.15 (m, 1H),
3.79 (s, 3H), 3.51 (s, 3H), 2.12 (s, 3H), 2.09 (s, 3H). 13C NMR (126 MHz,
CDCl3) δ 170.9, 170.5, 160.5, 123.1, 121.9, 118.9, 118.4, 95.2, 68.4,
63.2, 63.1, 55.3, 51.8, 21.0, 20.9. HRMS (ESI): m/z Calcd for
C15H19NNaO8 [M+Na]+: 364.1003, found 364.1005.
((2R,3R,6S)-3-acetoxy-6-(benzyloxy)-5-nitro-3,6-dihydro-2H-
pyran-2-yl)methyl acetate (3t):[14b] Colorless syrup. 1H NMR
(500 MHz, CDCl3) δ 7.36 (dd, J=8.7, 4.1 Hz, 5H), 7.29 (d, J=5.6 Hz,
1H), 5.78 (s, 1H), 5.40 (dd, J=5.6, 2.8 Hz, 1H), 4.84 (d, J=11.2 Hz,
1H), 4.73 (d, J=11.2 Hz, 1H), 4.49–4.45 (m, 1H), 4.28 (dd, J=11.5,
5.5 Hz, 1H), 4.23 (dd, J=11.5, 7.3 Hz, 1H), 2.12 (s, 3H), 2.09 (s, 3H).
Methyl (4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-ethoxy-2,4,6,7-
tetrahydro-pyrano[3,4-c]pyrrole-1-carboxylate (5f): Colorless syr-
up. [α]25 D=À 70.2 (c 2.11, CH2Cl2). 1H NMR (600 MHz, CDCl3) δ 9.21
(s, 1H), 6.89 (d, J=3.0 Hz, 1H), 6.26 (d, J=9.1 Hz, 1H), 5.69 (s, 1H),
4.29 (d, J=4.1 Hz, 2H), 4.22 (dt, J=8.5, 4.1 Hz, 1H), 3.90–3.85 (m,
1H), 3.79 (s, 3H), 3.71–3.65 (m, 1H), 2.11 (s, 3H), 2.09 (s, 3H), 1.29 (t,
J=7.1 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ 170.9, 170.5, 160.6,
123.2, 122.2, 118.9, 118.4, 94.0, 68.3, 63.6, 63.2, 63.1, 51.8, 21.0, 20.9,
15.3. HRMS (ESI): m/z Calcd for C16H21NNaO8 [M+Na]+: 378.1159,
found 378.1162.
((2R,3R,6S)-3-acetoxy-6-methoxy-5-nitro-3,6-dihydro-2H-pyran-2-
yl)methyl acetate (3u):[14b] Colorless syrup. 1H NMR (500 MHz,
CDCl3) δ 7.27 (d, J=4.2 Hz, 1H), 5.55 (s, 1H), 5.39 (dd, J=5.6, 2.8 Hz,
1H), 4.41–4.36 (m, 1H), 4.29–4.26 (m, 2H), 3.54 (s, 3H), 2.12 (s, 3H),
2.09 (s, 3H).
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(benzyloxy)-
2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate (5a): Color-
less syrup. [α]25 D=À 27.1 (c 2.00, CH2Cl2). IR (neat) vmax 3298, 3030,
1
2950, 1710, 1581, 1440, 1227, 1153, 1006, 729, 698 cmÀ 1. H NMR
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Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-isobutoxy-
4.22–4.17 (m, 1H), 3.79 (s, 3H), 2.48 (d, J=2.3 Hz, 1H), 2.12 (s, 3H),
2.08 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.9, 170.4, 160.5, 123.3,
121.2, 118.9, 118.7, 92.6, 79.2, 75.0, 68.7, 63.0, 54.6, 51.9, 20.9, 20.9.
HRMS (ESI): m/z Calcd for C17H19NNaO8 [M+Na]+: 388.1003, found
388.1008.
2,4,6,7-tetrahydro-pyrano[3,4-c]pyrrole-1-carboxylate (5g): Color-
less syrup. [α]25 D=À 15.6 (c 1.00, CH2Cl2). 1H NMR (500 MHz,
CDCl3) δ 9.35 (s, 1H), 6.88 (d, J=3.1 Hz, 1H), 6.25 (d, J=9.1 Hz, 1H),
5.65 (s, 1H), 4.28 (d, J=4.2 Hz, 2H), 4.23–4.17 (m, 1H), 3.79 (s, 3H),
3.58 (dd, J=9.3, 7.0 Hz, 1H), 3.38 (dd, J=9.3, 6.5 Hz, 1H), 2.11 (s,
3H), 2.09 (s, 3H), 1.92 (td, J=13.4, 6.7 Hz, 1H), 0.94 (d, J=6.7 Hz,
6H). 13C NMR (126 MHz, CDCl3) δ 170.8, 170.4, 160.5, 123.1, 122.1,
118.7, 118.3, 94.2, 75.0, 68.3, 63.2, 63.1, 51.7, 28.4, 20.9, 20.8, 19.5,
19.4. HRMS (ESI): m/z Calcd for C18H25NNaO8 [M+Na]+: 406.1472,
found 406.1484.
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(allyloxy)-
2,4,6,7-tetrahydropyrano [3,4-c]pyrrole-1-carboxylate (5m): Color-
less syrup. [α]25 D= +164.4 (c 1.81, CH2Cl2). IR (neat) vmax 3295,
3027, 2960, 1707, 1581, 1440, 1227, 1009, 726 cmÀ 1 1H NMR
.
(500 MHz, CDCl3) δ 9.30 (s, 1H), 6.90 (s, 1H), 6.27 (d, J=9.1 Hz, 1H),
5.98 (ddd, J=22.4, 10.9, 5.7 Hz, 1H), 5.72 (s, 1H), 5.33 (dd, J=17.2,
1.5 Hz, 1H), 5.22 (dd, J=10.4, 1.2 Hz, 1H), 4.31 (dd, J=10.8, 3.3 Hz,
1H), 4.28 (d, J=4.2 Hz, 2H), 4.25–4.20 (m, 1H), 4.17 (dd, J=12.8,
6.2 Hz, 1H), 3.79 (s, 3H), 2.12 (s, 3H), 2.09 (s, 3H). 13C NMR (126 MHz,
CDCl3) δ 170.9, 170.5, 160.5, 134.1, 123.3, 121.9, 118.9, 118.4, 117.7,
93.4, 68.7, 68.5, 63.2, 63.1, 51.9, 21.0, 21.0. HRMS (ESI): m/z Calcd for
C17H21NNaO8 [M+Na]+: 390.1159, found 390.1166.
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(hexyloxy)-
2,4,6,7-tetrahydro-pyrano[3,4-c]pyrrole-1-carboxylate (5h): Color-
less syrup. [α]25 D=À 18.7 (c 0.98, CH2Cl2). IR (neat) vmax 3307, 3030,
2953, 1738, 1440, 1233, 1009, 729 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ
9.29 (s, 1H), 6.88 (d, J=3.1 Hz, 1H), 6.26 (d, J=9.1 Hz, 1H), 5.67 (s,
1H), 4.31–4.26 (m, 2H), 4.23–4.18 (m, 1H), 3.84–3.80 (m, 1H), 3.79 (s,
3H), 3.59 (dt, J=9.5, 6.6 Hz, 1H), 2.11 (s, 3H), 2.09 (s, 3H), 1.63 (dd,
J=14.4, 7.4 Hz, 2H), 1.39–1.29 (m, 6H), 0.88 (t, J=6.9 Hz, 3H). 13C
NMR (126 MHz, CDCl3) δ 170.9, 170.5, 160.6, 123.2, 122.2, 118.8,
118.4, 94.1, 68.4, 68.3, 63.3, 63.2, 51.8, 31.7, 29.7, 26.0, 22.7, 21.0,
20.90, 14.1. HRMS (ESI): m/z Calcd for C20H29NNaO8 [M+Na]+:
434.1785, found 434.1775.
Methyl (4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(cinnamyloxy)-
2,4,6,7-tetrahydropyrano [3,4-c]pyrrole-1-carboxylate (5n): Color-
less syrup. [α]25 D=À 30.5 (c 1.12, CH2Cl2). IR (neat) vmax 3301, 3024,
2956, 1704, 1581, 1443, 1224, 1009, 741 cmÀ 1 1H NMR (500 MHz,
.
CDCl3) δ 9.31 (s, 1H), 7.39 (d, J=7.4 Hz, 2H), 7.32 (t, J=7.6 Hz, 2H),
7.24 (d, J=7.2 Hz, 1H), 6.92 (d, J=3.1 Hz, 1H), 6.66 (d, J=15.9 Hz,
1H), 6.38–6.32 (m, 1H), 6.29 (d, J=9.0 Hz, 1H), 5.79 (s, 1H), 4.48
(ddd, J=12.6, 5.7, 1.2 Hz, 1H), 4.37–4.33 (m, 1H), 4.33–4.29 (m, 2H),
4.29–4.24 (m, 1H), 3.80 (s, 3H), 2.13 (s, 3H), 2.09 (s, 3H). 13C NMR
(126 MHz, CDCl3) δ 170.9, 170.5, 160.5, 136.6, 133.3, 128.7, 128.0,
126.6, 125.2, 123.3, 122.0, 119.0, 118.4, 93.3, 68.5, 68.3, 63.2, 63.1,
51.9, 21.0, 21.0. HRMS (ESI): m/z Calcd for C23H25NNaO8 [M+Na]+:
466.1472, found 466.1473.
Methyl
oxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate
Colorless syrup. [α]25 D=À 79.2 (c 0.31, CH2Cl2). IR (neat) vmax 3313,
3030, 2950, 1729, 1443, 1227, 1009, 732, 569 cmÀ 1 1H NMR
(500 MHz, CDCl3) δ 9.37 (s, 1H), 6.92 (d, J=3.0 Hz, 1H), 6.25 (d, J=
8.0 Hz, 1H), 5.74 (s, 1H), 4.30–4.24 (m, 3H), 4.11 (dt, J=11.9, 6.1 Hz,
1H), 4.02–3.95 (m, 1H), 3.79 (s, 3H), 3.57 (td, J=6.1, 1.5 Hz, 2H), 2.12
(s, 3H), 2.09 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.9, 170.5, 160.5,
123.1, 121.3, 118.9, 118.6, 94.6, 68.8, 68.2, 63.2, 63.0, 51.9, 30.6, 21.0,
21.0. HRMS (ESI): m/z Calcd for C16H20BrNNaO8 [M+Na]+: 456.0264,
found 456.0273.
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(2-bromoeth-
(5i):
.
Methyl (4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(furan-2-ylmeth-
oxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate
(5o):
1
Colorless syrup. [α]25 D=À 24.3 (c 1.02, CH2Cl2). H NMR (500 MHz,
CDCl3) δ 9.20 (s, 1H), 7.42 (s, 1H), 6.86 (d, J=1.6 Hz, 1H), 6.40–6.34
(m, 2H), 6.28 (d, J=8.9 Hz, 1H), 5.78 (s, 1H), 4.75 (d, J=12.7 Hz, 1H),
4.67 (d, J=12.7 Hz, 1H), 4.32–4.23 (m, 3H), 3.79 (d, J=1.4 Hz, 3H),
2.13 (d, J=1.3 Hz, 3H), 2.08 (d, J=1.4 Hz, 3H). 13C NMR (126 MHz,
CDCl3) δ 170.9, 170.5, 160.5, 151.1, 143.1, 123.3, 121.5, 118.8, 118.6,
110.5, 109.8, 93.1, 68.5, 63.1, 63.0, 61.3, 51.8, 21.0, 21.0. HRMS (ESI):
m/z Calcd for C19H21NNaO9 [M+Na]+: 430.1109, found 430.1120.
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(2,2,2-
tribromoethoxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carbox-
1
ylate (5j): Colorless syrup. [α]25 D=À 7.3 (c 0.49, CH2Cl2). H NMR
(500 MHz, CDCl3) δ 9.36 (s, 1H), 7.01 (d, J=3.1 Hz, 1H), 6.29 (d, J=
9.2 Hz, 1H), 6.02 (s, 1H), 4.55 (d, J=11.7 Hz, 1H), 4.47 (d, J=11.7 Hz,
1H), 4.36–4.33 (m, 1H), 4.33–4.26 (m, 2H), 3.81 (s, 3H), 2.13 (s, 3H),
2.11 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.8, 170.5, 160.4, 123.3,
120.6, 118.9, 118.9, 94.6, 82.3, 69.4, 62.9, 51.9, 39.2, 21.0, 21.0. HRMS
(ESI): m/z Calcd for C16H18Br3NNaO8 [M+Na]+: 611.8475, found
611.8489.
Methyl
(6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(((3aS,5S,8bS)-
2,2,7,7-tetra-methyltetrahydro -5H-bis([1,3]dioxolo)[4,5-b:4’,5’-d]
pyran-5-yl)methoxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-
carboxylate (5p): Colorless syrup. [α]25 D=À 47.9 (c 2.07, CH2Cl2).
IR (neat) vmax 3304, 3030, 2987, 1729, 1440, 1372, 1230, 1064, 996,
726 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ 9.23 (s, 1H), 6.90 (d, J=2.9 Hz,
1H), 6.27 (d, J=9.1 Hz, 1H), 5.74 (s, 1H), 5.53 (d, J=5.0 Hz, 1H), 4.62
(dd, J=7.9, 2.0 Hz, 1H), 4.33–4.23 (m, 5H), 4.04 (t, J=6.3 Hz, 1H),
3.92 (dd, J=10.3, 6.6 Hz, 1H), 3.86–3.83 (m, 1H), 3.79 (s, 3H), 2.13 (s,
Methyl
(4S,6R,7S)-4-((9H-fluoren-9-yl)methoxy)-7-acetoxy-6-
(acetoxymethyl)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carbox-
ylate (5k): Colorless syrup. [α]25 D=À 8.3 (c 2.05, CH2Cl2). IR (neat)
vmax 3301, 3036, 2947, 1729, 1581, 1443, 1230, 1009, 726 cmÀ 1. H
1
NMR (500 MHz, CDCl3) δ 9.34 (s, 1H), 7.77 (d, J=7.5 Hz, 2H), 7.63
(dd, J=12.4, 7.5 Hz, 2H), 7.40 (t, J=6.6 Hz, 2H), 7.30 (q, J=7.5 Hz,
2H), 6.88 (d, J=3.0 Hz, 1H), 6.26 (d, J=8.7 Hz, 1H), 5.73 (s, 1H), 4.24
(dt, J=10.6, 4.0 Hz, 4H), 4.14 (dd, J=9.3, 7.4 Hz, 1H), 3.85 (dd, J=
9.3, 7.7 Hz, 1H), 3.81 (s, 3H), 2.13 (s, 3H), 1.93 (s, 3H). 13C NMR
(126 MHz, CDCl3) δ 170.8, 170.5, 160.5, 144.9, 144.6, 141.4, 141.3,
127.7, 127.7, 127.1, 127.0, 125.3, 125.3, 123.2, 122.0, 120.0, 120.0,
118.9, 118.5, 94.7, 70.8, 68.8, 63.1, 51.9, 47.9, 21.0, 20.7. HRMS (ESI):
m/z Calcd for C28H27NNaO8 [M+Na]+: 528.1629, found 528.1639.
3H), 2.08 (s, 3H), 1.50 (s, 3H), 1.45 (s, 3H), 1.35 (s, 3H), 1.32 (s, 3H). 13
C
NMR (126 MHz, CDCl3) δ 171.0, 170.4, 160.5, 123.3, 122.0, 118.8,
118.5, 109.4, 108.7, 96.5, 94.2, 71.1, 70.8, 70.7, 68.5, 66.5, 66.2, 63.0,
63.0, 51.8, 26.1,26.1, 25.0, 24.7, 21.0. HRMS (ESI): m/z Calcd for
C26H35NNaO13 [M+Na]+: 592.2001, found 592.2007.
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-
(((3S,8S,9S,10R,13R,14S,17R)-10,13-dimethyl-
ylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-
17-((R)-6-meth-
tetradecahy-
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(prop-2-yn-1-
dro-1H-cyclopenta[a]phenanthren-3-yl)oxy)-2,4,6,7-tetrahydro-
yloxy)-2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate (5l):
Colorless syrup. [α]25 D=À 11.3 (c 1.00, CH2Cl2). IR (neat) vmax 3283,
pyrano[3,4-c]pyrrole-1-carboxylate (5q): White solid. [α]25 D=
1
À 7.6 (c 1.03, CH2Cl2). H NMR (500 MHz, CDCl3) δ 9.24 (s, 1H), 6.86
3030, 2953, 1707, 1443, 1230, 1156, 1006, 732, 606 cmÀ 1. H NMR
(d, J=2.9 Hz, 1H), 6.27–6.21 (m, 1H), 5.83 (s, 1H), 5.37 (d, J=4.6 Hz,
1H), 4.28 (s, 3H), 3.79 (s, 3H), 3.72–3.63 (m, 1H), 2.39 (t, J=7.0 Hz,
2H), 2.10 (s, 3H), 2.09 (s, 3H), 1.98 (d, J=21.2 Hz, 3H), 1.91–0.68 (m,
1
(500 MHz, CDCl3) δ 9.40 (s, 1H), 6.91 (d, J=3.0 Hz, 1H), 6.28 (d, J=
9.2 Hz, 1H), 5.87 (s, 1H), 4.40–4.34 (m, 2H), 4.28 (d, J=4.0 Hz, 2H),
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38H). 13C NMR (126 MHz, CDCl3) δ 171.0, 170.6, 160.6, 140.8, 123.3,
122.5, 122.0, 118.9, 118.1, 92.3, 68.3, 63.38, 63.2, 56.8, 56.2, 51.8,
50.3, 42.4, 40.3, 39.9, 39.6, 37.3, 36.8, 36.3, 35.9, 32.0, 32.0, 28.3, 28.3,
28.10, 24.4, 23.9, 22.9, 22.7, 21.2, 21.0, 19.4, 18.8, 12.0. HRMS (ESI):
m/z Calcd for C41H61NNaO8 [M+Na]+: 718.4289, found 718.4295.
Acknowledgements
We thank the analytic center of East China Normal University for
spectroscopic measurements. This project was partly financially
supported by Natural Science Foundation of Shanghai
(11ZR1410400).
Methyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-isopropoxy-
2,4,6,7-tetrahydro-pyrano[3,4-c]pyrrole-1-carboxylate (5r): Color-
less syrup. [α]25 D=À 16.0 (c 0.70, CH2Cl2). IR (neat) vmax 3301, 3033,
2953, 1704, 1440, 1369, 1224, 996, 735 c 1H NMR (500 MHz, CDCl3) δ
9.24 (s, 1H), 6.85 (d, J=3.0 Hz, 1H), 6.25 (d, J=9.0 Hz, 1H), 5.77 (s,
1H), 4.30–4.20 (m, 3H), 4.14–4.06 (m, 1H), 3.79 (s, 3H), 2.11 (s, 3H),
2.08 (s, 3H), 1.28–1.25 (m, 6H). 13C NMR (126 MHz, CDCl3) δ 170.9,
170.5, 160.6, 123.3, 122.6, 118.9, 118.1, 92.5, 70.0, 68.3, 63.3, 63.2,
51.8, 23.5, 22.1, 21.0, 20.9. HRMS (ESI): m/z Calcd for C17H23NNaO8
[M+Na]+: 392.1316, found 392.1319.
Conflict of Interest
The authors declare no conflict of interest.
Keywords: 2-nitroglycals · Ferrier rearrangement · Barton-Zard
reaction · N-heterocyclic carbene · One-pot
Methyl (4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(cyclohexyloxy)-
2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate (5s): Color-
less syrup. [α]25 D=À 12.8 (c 0.63, CH2Cl2). IR (neat) vmax 3301, 3033,
2929, 1732, 1440, 1227, 1000, 735 cmÀ 1. 1H NMR (500 MHz, CDCl3) δ
9.21 (s, 1H), 6.84 (d, J=3.0 Hz, 1H), 6.24 (dd, J=5.3, 3.5 Hz, 1H), 5.82
(s, 1H), 4.30–4.25 (m, 3H), 3.81–3.73 (m, 4H), 2.11 (s, 3H), 2.08 (s, 3H),
1.98 (t, J=12.7 Hz, 2H), 1.79–1.73 (m, 2H), 1.40–1.27 (m, 6H). 13C
NMR (126 MHz, CDCl3) δ 170.9, 170.5, 160.5, 123.3, 122.6, 118.8,
118.2, 92.4, 76.0, 68.3, 63.4, 63.2, 51.8, 33.7, 32.2, 25.7, 24.6, 24.3,
21.0, 20.9. HRMS (ESI): m/z Calcd for C20H27NNaO8 [M+Na]+:
432.1629, found 432.1641.
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Yusulf, Z. F. Wang, J. B. Zhang, J. Tang, Chin. Chem. Lett. 2010, 21, 922–
926; e) J. Zhou, B. Zhang, G. Yang, X. Chen, Q. Wang, Z. Wang, J. Zhang,
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Methyl
(4S,6R,7R)-7-acetoxy-6-(acetoxymethyl)-4-(benzyloxy)-
2,4,6,7-tetrahy-dropyrano [3,4-c]pyrrole-1-carboxylate (5t): White
1
solid. [α]25 D=À 20.8 (c 0.36, CH2Cl2). H NMR (500 MHz, CDCl3) δ
9.27 (s, 1H), 7.41–7.34 (m, 4H), 7.30 (ddd, J=7.0, 3.8, 1.5 Hz, 1H),
6.88 (d, J=3.1 Hz, 1H), 6.28 (d, J=9.0 Hz, 1H), 5.78 (s, 1H), 4.86 (d,
J=11.8 Hz, 1H), 4.70 (d, J=11.8 Hz, 1H), 4.27 (dq, J=7.3, 5.7 Hz,
2H), 4.20 (d, J=9.5 Hz, 1H), 3.79 (s, 3H), 2.11 (s, 3H), 2.09 (s, 3H). 13C
NMR (126 MHz, CDCl3) δ 170.9, 170.5, 160.5, 137.6, 128.6, 128.1,
128.0, 123.3, 121.9, 118.9, 118.5, 93.4, 69.8, 68.6, 63.1, 63.1, 51.9,
21.0, 21.0. HRMS (ESI): m/z Calcd for C21H23NNaO8 [M+Na]+:
440.1316, found 440.1315.
Methyl
(4S,6R,7R)-7-acetoxy-6-(acetoxymethyl)-4-methoxy-
2,4,6,7-tetrahydro-pyrano[3,4-c]pyrrole-1-carboxylate (5u): White
solid. [α]25 D= +28.0 (c 0.24, CH2Cl2). H NMR (500 MHz, CDCl3) δ
1
9.35 (s, 1H), 6.94 (d, J=3.0 Hz, 1H), 6.26 (d, J=2.0 Hz, 1H), 5.68 (s,
1H), 4.43 (ddd, J=8.1, 3.8, 2.1 Hz, 1H), 4.36 (dd, J=11.6, 4.0 Hz, 1H),
4.19 (dd, J=11.6, 8.2 Hz, 1H), 3.81 (s, 3H), 3.51 (s, 3H), 2.11 (s, 3H),
2.07 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 170.8, 170.1, 160.8, 121.1,
121.1, 119.3, 118.7, 95.2, 68.2, 63.3, 61.7, 55.2, 51.8, 21.0, 21.0. HRMS
(ESI): m/z Calcd for C15H19NNaO8 [M+Na]+: 364.1003, found
364.1000.
ethyl
(4S,6R,7S)-7-acetoxy-6-(acetoxymethyl)-4-(benzyloxy)-
2,4,6,7-tetrahydropyrano[3,4-c]pyrrole-1-carboxylate (5v): Color-
less syrup. [α]25 D=À 22.8 (c 2.16, CH2Cl2). 1H NMR (500 MHz,
CDCl3) δ 9.33 (s, 1H), 7.40–7.33 (m, 4H), 7.32–7.27 (m, 1H), 6.86 (d,
J=3.0 Hz, 1H), 6.30–6.25 (m, 1H), 5.78 (s, 1H), 4.85 (d, J=11.8 Hz,
1H), 4.69 (d, J=11.8 Hz, 1H), 4.37–4.32 (m, 1H), 4.24 (dddd, J=23.3,
14.2, 7.7, 4.5 Hz, 4H), 2.10 (s, 3H), 2.09 (s, 3H), 1.30 (t, J=7.1 Hz, 3H).
13C NMR (126 MHz, CDCl3) δ 170.97, 170.55, 160.04, 137.73, 128.62,
128.15, 127.98, 123.11, 121.84, 119.23, 118.22, 93.47, 69.75, 68.85,
63.28, 63.20, 60.94, 21.10, 20.99, 14.54. HRMS (ESI): m/z Calcd for
C22H25NNaO8 [M+Na]+: 454.1472, found 454.1479.
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Full Papers
doi.org/10.1002/cctc.202100795
ChemCatChem
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Manuscript received: June 1, 2021
Revised manuscript received: July 15, 2021
Accepted manuscript online: July 18, 2021
Version of record online: ■■■, ■■■■
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FULL PAPERS
Dr. N. Jiang, Dr. Y. Mei, Dr. Y. Yang,
Dr. Y. Dong, Dr. Z. Ding, Prof. J.
Zhang*
1 – 11
A General Strategy for the Stereo-
selective Synthesis of Pyrrole-
Fused Chiral Skeletons: [3+2] Cy-
cloaddition with 2-Nitro-2,3-Un-
saturated Glycosides
Carbohydrate Chemistry: the first
NHC-catalyzed stereoselective
synthesis of 2-nitro-2,3- unsaturated
glycosides under mild reaction condi-
tions is reported. The synthesis of
chiral pyrrole in one-pot is transition-
metal-free and has a broad substrate
scope with high yields and excellent
stereoselective.