A convenient and highly stereoselective method for synthesis of octahydropyrano[3,2-b]pyrrole derivatives

Article abstract of DOI:10.1016/j.carres.2012.11.016

The octahydropyrano[3,2-b]pyrrole derivatives are synthesized by a double reductive amination from pyranose derivatives of nono-2,5-diuloses and octos-4-uloses and various amines. The cyclization proceeded smoothly in the presence of sodium triacetoxyborohydride to produce a series of novel fused N-heterobicyclic compounds with high stereoselectivity.

Full text of DOI:10.1016/j.carres.2012.11.016

Carbohydrate Research 366 (2013) 55–62
Contents lists available at SciVerse ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
A convenient and highly stereoselective method for synthesis
of octahydropyrano[3,2-b]pyrrole derivatives
Xiaofeng Ma a,c, Qin Tang a,c, Jun Ke a,c, Haibo Wang a,c, Wei Zou b, Huawu Shao a,
⇑
a Natural Product Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
b Institute for Biological Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario, Canada K1A 0R6
c Graduate School of Chinese Academy of Sciences, Beijing 100039, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 August 2012
Received in revised form 29 October 2012
Accepted 19 November 2012
Available online 29 November 2012
The octahydropyrano[3,2-b]pyrrole derivatives are synthesized by a double reductive amination from
pyranose derivatives of nono-2,5-diuloses and octos-4-uloses and various amines. The cyclization pro-
ceeded smoothly in the presence of sodium triacetoxyborohydride to produce a series of novel fused
N-heterobicyclic compounds with high stereoselectivity.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Pyrrolidine
Fused bicyclic compound
Pyrrole derivatives
Stereoselective synthesis
Cyclization
1. Introduction
Bäcklund rearrangement using glycosyl sulfones3a,9 and conjugate
addition of carbanions to 2-nitroglycals.5a,10
Polyhydroxylated 2-N-acetamidosugar are potential glycosi-
dase inhibitors, castanospermine and swainsonine are the two
examples that are mostly studied. In contrast, octahydropyr-
ano[3,2-b]pyrroles have so far attracted less interest as glycosidase
inhibitors, probably due to lack of effective synthetic methods. 2-
Octahydropyrano[3,2-b]pyrrole, which combines a pyrrole seg-
ment to 2-amino-C-glycoside backbone, is a potential glycosidase
inhibitor. Actually, castanospermine is the analogue of octahydro-
pyrano[3,2-b]pyrrole and an efficient glycosidase inhibitors (Fig-
ure 1a)11 and a variety of analogues of castanospermine (Fig. 1b)
Acetamido-2-deoxy-
D-glycopyranosides subunits constitute the
have been identified as specific inhibitors of b-D
-galactosidase.12
core structural elements prevalent in a large number of living
organisms as oligosaccharides and glycoconjugates, and could
serve as metabolic substrates for cell surface engineering.1 To
understand these biological processes, considerable studies on
the modification of 2-N-acetamidosugar residues were performed
during the last decade2 and change O-glycoside to C-glycoside at-
tracted more attention in glycochemistry3 and glycobiology,4 since
these carbohydrate mimics possess an improved stability towards
acid, base and enzymatic hydrolysis, and display interesting bio-
logical activity.4 However, nitrogen-based groups such as amides,
carbamates and azides are incompatible under conventional C-gly-
cosylation conditions, so C-glycosylation of 2-amino sugar has
been regarded as one of the most difficult modifications.4,5 The
strategies for the construction of 2-amino-C-glycosides include
Wittig reactions with sugar lactols,6 radical coupling between gly-
cosyl Se5d–f,7 or X (Br, Cl)8 and activated alkenes, or Ramberg–
Octahydropyrano[3,2-b]pyrrole derivatives were often synthe-
sized by radical cyclization reaction using glycosyl Se as radical
precursors,7 or intramolecular hydrogen atom transfer reaction
promoted by N-radicals via C-glycosides phosphoramidates.13 In
2005, Wang and co-workers developed an alternative method via
1,5-anhydro-6-bromo-4-O-methyl-sulfonyl-D-glucitol through 12
steps.14 In 2007, Schweizer and co-workers reported a simpler
method via 2-amino-2-deoxy-C-glycoside.15 Furthermore, 2-ni-
tro-b-C-glycosides, which were obtained by conjugate addition of
carbanions to 2-nitroglycals, can be converted to trans-fusion of
bicyclic lactam analogue, but this conjugate addition reaction only
given the mixture C-glycosides of anomeric isomers.5a Vankar and
cooperators have recently obtained bicyclic pyrrolidines via
sequential intermolecular and intramolecular nucleophilic substi-
tutions.16 However, only four different bicyclic products were
afforded by this procedure.
Reductive amination is an efficient method for C–N bond forma-
tion and has been successfully used in synthesis of 2 and 3-N-pyr-
rolidine derivatives of glycosides.12,17 However, there are no
⇑
Corresponding author.
E-mail address: shaohw@cib.ac.cn (H. Shao).
0008-6215/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.carres.2012.11.016

56
X. Ma et al. / Carbohydrate Research 366 (2013) 55–62
Table 1
OH
OH
Conditions optimization of the double reductive aminationa
OH
O
OMe
H
H
HO
HO
OBn
OBn
R
N
N
HO
H
O
O
BnO
BnO
n-butylamine 5a
b: Previous compoundref12
N
condition
BnO
a: Castanospermine
O
O
OBn
6a
Figure 1. The structures of castanospermine (a) and previous compound (b).
3
OBn
Entry
Reductant (equiv)
HOAc (equiv)
Solvent
Yieldb (%)
OBn
Hg(OAc)2
O
O
1
2
3
4
5
6
7
8
9
10
4
4
4
4
3.5
3
2.5
2
3
3
2
2
2
2
2
2
2
2
1
0
ClCH2CH2Cl
THF
62
50
48
70
67
70
23
Trace
NR
Trace
BnO
BnO
BnO
BnO
Jones reagents
CH3CN
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
OH
1
O
O
3
IBX
DMSO
OBn
OBn
O
1) O3, DCM
2) Zn, HOAc
O
O
BnO
BnO
BnO
BnO
a
All reactions were performed with diketone 3 (0.20 mmol), n-butylamine 5a
(0.22 mmol) under a N2 atmosphere, in solvent (0.7 mL) at room temperature
overnight.
O
O
4
2
b
Isolated yield.
Scheme 1. Synthesis of glycosyl-1,4-dicarbonyl compounds 3 and 4.
the less strained cis-fused bicycle with the newly formed C–N bond
in equatorial orientation, while the methyl group at C-2 adopts an
exo-disposition on the bicyclic system by steric reasons. This is
confirmed by NOESY interactions between methyl group and H-
7a, H-3a in compound 6a as shown in Figure 2.
Encouraged by the initial success, we decided to explore the
applicability of the double reductive amination to a number of
amines including aliphatic amines such as benzylamine (5b), 2-
aminoethanol (5c), octylamine (5d), hexylamine (5e) and 4-flu-
oro-phenethylamine (5f) (Table 2, entries 1–5), and aromatic
amine including aniline (5g), p-toluidine (5h) and o-toluidine (5i)
(Table 2, entries 6–8). To our delight, the expected octahydropyr-
ano[3,2-b]pyrrole derivatives were obtained in 53–76% yields. Sur-
prisingly, in all product only one diastereoisomer was obtained as a
major product except for 2-aminoethanol (Table 2, entry 2), aniline
(Table 2, entry 6) and p-toluidine (Table 2, entry 7).20
In order to obtain better results for synthesis of pyrrole deriva-
tives and expand molecular libraries of these compounds, the fea-
sibility was further studied with keto-aldehyde derivative 4.
Logically, keto-aldehyde 4 was subjected to the double reductive
amination procedure using a range of primary amines, and a series
of other octahydropyrano[3,2-b]pyrrole derivatives were prepared
in 42–67% yields (Table 2, entries 9–15).
In summary, we have developed a mild and efficient method for
the stereoselective synthesis of octahydropyrano[3,2-b]pyrrole
derivatives from C-glycosides. The method is applied to the syn-
thesis of castanospermine analogues. Further investigations of
the scope of this reaction and of the biological activities of these
compounds will be undertaken.
reports on the synthesis of octahydropyrano[3,2-b]pyrrole using
reductive amination. Therefore, it is necessary to develop a highly
stereoselective and convenient method for the synthesis of octahy-
dropyrano[3,2-b]pyrrole derivatives. As part of our continuing
interest in the development of new synthetic methodologies,18,19
we disclose our results on the highly stereoselective synthesis of
octahydropyrano[3,2-b]pyrrole derivatives via double reductive
amination of glycosyl-1,4-dicarbonyl compounds using NaB-
H(OAc)3 in dichloromethane at room temperature.
2. Results and discussion
1,4-Dicarbonyl compound 3 was prepared by oxidization of 2-
OH and C@C bond of alkene 1, using Hg(OAc)2 and Jones reagent
in 76% yield and 1,4-dicarbonyl compound 4 was obtained in
two steps by oxidization of 2-OH of alkene 1 using IBX to afford al-
kene ketone 2 followed by ozonolysis and in situ reduction of the
ozonide using Zn powder and HOAc in 72% total yield (Scheme 1).
With compounds 3 and 4 in hand, the construction of octahydro-
pyrano[3,2-b]pyrrole via reductive amination was carried out.
Initial studies were performed with NaCNBH3 in MeOH using n-
butylamine as aminating reagent at 0 °C,17a but the reaction was so
complex that no major product could be detected by TLC. Then,
NaBH(OAc)3, which is a powerful and versatile reducing reagent
for the reductive amination, was used (Table 1). In order to find a
suitable condition for our experiments, an optimization on the sol-
vent, the amounts of NaBH(OAc)3 and HOAc were executed. Fortu-
nately, the reaction could proceed smoothly in all solvents
including dichloroethane, dichloromethane, acetonitrile and tetra-
hydrofuran. Dichloromethane was the best solvent (Table 1, entry
4), and dichloroethane was also efficient (Table 1, entry 1), while
the acetonitrile (Table 1, entry 3) and tetrahydrofuran (Table 1, en-
try2) were not as good as the former solvents. After variation of the
amount of reducing agent and acetic acid, it was found that the
double reductive amination could be proceeded smoothly with
3.0 equiv of NaBH(OAc)3 and 2.0 equiv of HOAc in CH2Cl2 at room
temperature (Table 1, entry 6).
3. Experimental
All reagents were purchased from commercial suppliers and
used without further purification unless otherwise noted. Reac-
tions were monitored by thin layer chromatography using silica
gel HSGF254 plates (0.20–0.25 mm thickness) with a fluorescent
indicator. Visualization on TLC was achieved by UV light
(254 nm) and a typical TLC indicator solution (5% sulfuric acid/eth-
anol solution). Column chromatography was performed on silica
gel 90, 200–300 mesh. Optical rotations were measured with a
The stereochemistry of new stereocenters in compound 6a was
confirmed by 1H NMR and NOESY spectra. The cyclization leads to

X. Ma et al. / Carbohydrate Research 366 (2013) 55–62
57
H3a
½
a 2D0 +55.7 (c 0.5, CHCl3); 1H NMR (600 MHz, CDCl3): d 9.67 (s,
ꢁ
OBn
NOE
1H), 7.47–7.11 (m, 15H), 5.00 (d, J = 11.5 Hz, 1H), 4.83 (d,
J = 11.4 Hz, 2H), 4.69 (d, J = 11.6 Hz, 3H), 4.50 (d, J = 11.4 Hz, 1H),
4.45 (d, J = 11.9 Hz, 1H), 4.35 (d, J = 12.0 Hz, 1H), 4.00 (d,
J = 8.2 Hz, 1H), 3.62 (d, J = 10.4 Hz, 1H), 3.55 (d, J = 10.5 Hz, 1H),
2.97–2.79 (m, 2H); 13C NMR (150 MHz, CDCl3): d 209.0, 197.9,
138.0, 137.8, 137.6(2), 128.5, 128.4(2), 128.3, 128.2, 128.1,
127.9(2), 127.8, 127.7(2), 84.1, 76.0, 74.7, 74.2, 74.1, 73.4, 70.0,
45.1; ESI-HRMS: m/z calcd for C29H30NaO6 [M+Na]+: 497.1935,
found 497.1940.
O
5
2
7
N
BnO
n-Bu
H7a
BnO
NOE
Figure 2. The NOEs of compound 6a.
Perkin Elmer-341 Digital Polarimeter. 1H NMR and 13C NMR (600
and 150 MHz, respectively) spectra were recorded with a Bruker
Avance 600 spectrometer. 1H NMR chemical shifts are reported
in ppm (d) relative to tetramethylsilane (TMS) with the solvent res-
onance employed as the internal standard (CDCl3, d = 7.26 ppm).
Data are reported as follows: chemical shift, multiplicity (s = sin-
glet, d = doublet, t = triplet, m = multiplet), coupling constants
(Hz) and integration. 13C NMR chemical shifts are reported in
ppm from tetramethylsilane (TMS) with the solvent resonance as
the internal standard (CDCl3, d = 77.0 ppm). ESI-HRMS spectra
were recorded on BioTOF Q.
3.3. General procedure for synthesis of octahydropyrano[3,2-
b]pyrrole derivatives
To a solution of diketone 3 (98.0 mg, 0.201 mmoL) or keto-alde-
hyde 4 (95.0 mg, 0.2 mmoL) in CH2Cl2 (0.7 mL) were successively
added AcOH (23 lL, 0.4 mmoL), and primary amine (0.22 mmoL)
and NaBH(OAc)3 (138 mg, 0.60 mmoL). The mixture was stirred
at room temperature under a N2 atmosphere until the reactants
were consumed as determined by TLC analysis. The reaction mix-
ture was concentrated and purified by silica gel column chroma-
tography (Petroleum ether/EtOAc/TEA = 80:20:1–50:50:1).
3.1. 4,8-Anhydro-6,7,9-tri-O-benzyl-1,3-dideoxy-D-manno-
nono-2,5-diulose (3)
3.4. (2R,3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-1-butyl-2-methyl-octahydropyrano[3,2-b]pyrrole (6a)
To a solution of 1 (1.0 g, 2.11 mmol) and Hg(OAc)2 (236 mg,
0.74 mmol) in acetone/water (4:1, 10 mL) was added dropwise at
0 °C a solution of Jones reagent (2 M, 5.9 mL). The dark greenish-
brown mixture was stirred for 4 h at 0 °C and 2 mL i-propanol
was added and the reaction mixture was kept stirring until the
dark greenish-brown mixture became deep green, and then the
reaction mixture poured into water (10 mL). The aqueous mixture
was extracted with EtOAc (3 ꢀ 15 mL). Usual workup and chroma-
tography (Petroleum ether/EtOAc = 3:1) afforded 3 as a colourless
syrup (0.78 g, 1.60 mmol, 76%).
Yield: 74.1 mg, 0.14 mmol, 70%. Light red syrup: ½a D20
ꢁ
+41.2 (c
0.2, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.39–7.19 (m, 15H),
4.88 (d, J = 11.4 Hz, 1H), 4.84 (d, J = 11.4 Hz, 1H), 4.72 (d,
J = 11.1 Hz, 1H), 4.56 (d, J = 12.2 Hz, 1H), 4.47 (dd, J = 17.7,
11.7 Hz, 2H), 4.40 (dd, J = 15.0, 7.5 Hz, 1H), 3.86–3.80 (m, 1H),
3.69 (t, J = 7.5 Hz, 1H), 3.65–3.55 (m, 3H), 2.84 (t, J = 6.8 Hz, 1H),
2.74–2.59 (m, 3H), 2.13–2.05 (m, 1H), 1.72–1.57 (m, 1H), 1.47–
1.36 (m, 2H), 1.19 (dd, J = 14.3, 6.9 Hz, 2H), 1.13 (d, J = 5.9 Hz,
3H), 0.83 (t, J = 7.4 Hz, 3H); 13C NMR (150 MHz, CDCl3): d 138.9,
138.3, 128.3(2), 128.0, 127.8, 127.7, 127.6, 127.5, 127.4, 83.9,
77.9, 74.3, 74.2, 73.9, 73.7, 73.4, 70.0, 67.2, 56.9, 53.1, 37.7, 29.7,
21.2, 20.7, 14.1; ESI-HRMS: m/z calcd for C34H44NO4 [M+H]+:
530.3270, found 580.3292.
½
a 2D0 +20.4 (c 0.6, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.49–7.20
ꢁ
(m, 15H), 5.03 (d, J = 11.5 Hz, 1H), 4.85 (d, J = 11.5 Hz, 1H), 4.79 (d,
J = 9.7 Hz, 1H), 4.70 (d, J = 11.5 Hz, 1H), 4.55 (t, J = 4.9 Hz, 1H), 4.51
(d, J = 11.5 Hz, 1H), 4.46 (d, J = 12.0 Hz, 1H), 4.35 (d, J = 12.0 Hz,
1H), 4.07–4.00 (m, 1H), 3.95 (dd, J = 9.6, 7.1 Hz, 1H), 3.60 (dd,
J = 10.6, 2.6 Hz, 1H), 3.54 (dd, J = 10.6, 4.4 Hz, 1H), 2.94 (d,
J = 5.0 Hz, 2H), 2.16 (s, 3H); 13C NMR (150 MHz, CDCl3): d 209.8,
204.4, 137.9, 137.8, 137.7 128.4(3), 128.3, 128.2, 127.9, 127.8,
127.7, 84.5, 77.3, 76.1, 75.5, 74.2, 74.0, 73.4, 70.0, 45.4, 30.0; ESI-
3.5. (2R,3aR,5R,6S,7R,7aS)-1-Benzyl-6,7-bis(benzyloxy)-5-
[(benzyloxy)methyl]-2-methyl-octahydropyrano[3,2-b]pyrrole
(6b)
HRMS: m/z calcd for
C
30H32NaO6 [M+Na]+: 511.2097, found
Yield: 69.8 mg, 0.124 mmol, 62%. Light red syrup: ½a D20
ꢁ
+30.0 (c
511.2091.
0.4, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.28 (m, 20H), 4.81 (d,
J = 11.4 Hz, 1H), 4.67 (d, J = 11.4 Hz, 1H), 4.63 (d, J = 11.3 Hz, 1H),
4.55 (d, J = 12.3 Hz, 1H), 4.48 (d, J = 12.3 Hz, 1H), 4.39 (dd, J = 9.0,
6.1 Hz, 2H), 4.00 (d, J = 14.6 Hz, 1H), 3.95–3.90 (m, 1H), 3.81 (t,
J = 6.6 Hz, 1H), 3.73 (d, J = 14.6 Hz, 1H), 3.63–3.58 (m, 3H), 2.92
(t, J = 6.6 Hz, 1H), 2.61 (dd, J = 15.9, 6.1 Hz, 1H), 2.23–2.09 (m,
1H), 1.61 (dd, J = 21.4, 8.6 Hz, 1H), 1.00 (d, J = 6.0 Hz, 3H); 13C
NMR (150 MHz, CDCl3): d 139.2, 138.7, 138.3(2), 129.1, 128.3,
128.0, 127.9, 127.8, 127.8, 127.7, 127.6, 126.7, 82.4, 77.8, 73.7,
73.7, 73.6, 73.5, 73.4, 70.2, 67.4, 58.0, 57.0, 38.6, 20.6; ESI-HRMS:
m/z calcd for C37H42NO4 [M+H]+: 564.3114, found 564.3116.
3.2. 3,7-Anhydro-5,6,8-tri-O-benzyl-2-deoxy-D-manno-octos-4-
ulose (4)
To a stirred solution of 1 (7.6 g, 15.9 mmol) in DMSO (20 mL)
was added IBX in DMSO (9.0 g, 32.0 mmol, 20 mL). The reaction
mixture was allowed to stir at room temperature for 2.5 h. The
mixture was diluted with CH2Cl2 (60 mL), extracted with water
(40 mL) and filtered over celit. The organic layer was collected,
and the aqueous layer was re-extracted with further CH2Cl2
(2 ꢀ 20 mL). The combined organic phase was dried over anhy-
drous Na2SO4 and concentrated to give colourless syrup (7.0 g) 2.
To a solution of ketone 2 in CH2Cl2 (150 mL) was cooled in
ꢂ78 °C. A stream of ozone was passed into the solution through
a sintered-glass sprayer. When the starting material disappeared
(about 30 min), the solution was concentrated to a residue. To
the above residue in glacial acetic acid (151 mL) was added zinc
dust (3.2 g, 49.0 mmol) and the mixture was stirred at room tem-
perature overnight. Usual workup and chromatographic purifica-
tion (Petroleum ether/EtOAc 3:1) afforded 4 as a white solid
(5.43 g, 11.4 mmol, 72%).
3.6. (3aR,5R,6S,7R,7aS)-1-Hydroxyethyl-6,7-bis(benzyloxy)-5-
[(benzyloxy)-methyl]-2-methyl-octahydropyrano[3,2-b]pyrrole
(6c)
Yield: 54.8 mg, 0.106 mmol, 53%, major:minor = 3:1. Light red
syrup: ½a 2D0
ꢁ
+27.8 (c 0.7, CHCl3); 1H NMR (600 MHz, CDCl3): d
7.57–6.99 (m, 15H), 4.75 (d, J = 11.7 Hz, 1H), 4.66 (d, J = 11.7 Hz,
1H), 4.65–4.57(m, 1H), 4.52 (t, J = 11.4 Hz, 2H), 4.50–4.44 (m, 2H),
4.41 (t, J = 11.5 Hz, 1H), 3.92–3.86 (m, 1H), 3.70 (dd, J = 14.7,

58
X. Ma et al. / Carbohydrate Research 366 (2013) 55–62
Table 2
Synthesis of octahydropyrano[3,2-b]pyrrole derivatives from glycosyl-1,4-dicarbonyl compoundsa
OBn
O
OBn
O
R2NH2, AcOH, NaBH(OAc)3
CH2Cl2, rt
BnO
BnO
R1
O
BnO
O
N
OBn R2
R1
6b-6p
R1 = Me, 3
R1 = H, 4
Entry
R1
R2NH2
Products
Time (h)
Yieldb (%)
OBn
O
NH2
5b
N
1
Me
BnO
26
62
OBn
6b
NH2
OBn
HO
O
5c
2
Me
20
53c
N
BnO
OBn
6c
OH
OBn
NH2
6
O
5d
3
4
Me
Me
16
16
55
63
N
N
BnO
OBn
6
4
6d
OBn
NH2
4
O
5e
BnO
OBn
6e
NH2
OBn
O
N
BnO
OBn
5
Me
16
59
6f
F
5f
F
NH2
OBn
O
6
7
Me
Me
26
20
64d
N
N
5g
BnO
OBn
6g
NH2
OBn
O
BnO
76e
5h
OBn
6h

X. Ma et al. / Carbohydrate Research 366 (2013) 55–62
59
Table 2 (continued)
Entry
R1
R2NH2
Products
Time (h)
Yieldb (%)
NH2
OBn
O
8
9
Me
16
58
5i
N
N
BnO
OBn
6i
OBn
O
NH2
2
H
11
55
BnO
5a
OBn
6j
NH2
OBn
HO
O
5c
10
11
12
H
H
H
11
11
11
64
42
54
N
BnO
OBn
6k
OH
OBn
NH2
6
5d
O
N
N
N
BnO
OBn
6
6l
OBn
NH2
4
5e
O
BnO
OBn
4
6m
NH2
OBn
O
BnO
OBn
13
H
11
53
6n
F
5f
F
NH2
OBn
O
N
N
14
H
BnO
13
62
5h
OBn
6o
NH2
OBn
O
OMe
BnO
15
H
11
67
OBn
6p
5j
MeO
a
Reaction conditions: In all cases, the productwas obtained by using : dicarbonyl compounds 3 or 4 (0.20 mmol), AcOH (23 lL, 0.4 mmol), amine (0.22 mmol), NaBH(OAc)3
(138 mg, 0.60 mmol), 0.7 mL CH2Cl2.
b
Isolated yield.
c
Major/Minor = 3:1 (values were determined by 1H NMR).
d
Major/Minor = 3:2 (values were determined by 1H NMR).
e
Major/Minor = 1:1 (Values were determined by 1H NMR).

60
X. Ma et al. / Carbohydrate Research 366 (2013) 55–62
9.2 Hz, 1H), 3.62–3.47 (m, 4H), 2.83 (t, J = 6.3 Hz, 1H), 2.75 (d,
J = 9.2 Hz, 1H), 2.66–2.55 (m, 1H), 2.18 (dd, J = 13.3, 7.0 Hz, 1H),
1.65 (dd, J = 18.6, 11.4 Hz, 1H), 1.26 (s, 1H), 1.16 (d, J = 6.1 Hz,
2H), 6.92–6.87 (m, 1H), 6.82 (d, J = 8.1 Hz, 1H), 6.73 (t, J = 7.2 Hz,
1H), 6.66 (t, J = 7.2 Hz, 1H), 4.87 (d, J = 10.7 Hz, 1H), 4.76–4.72 (m,
1H), 4.71 (d, J = 8.1 Hz, 2H), 4.68 (d, J = 1.8 Hz, 1H), 4.60 (d,
J = 12.2 Hz, 2H), 4.56 (dd, J = 11.5, 5.4 Hz, 3H), 4.51 (d, J = 10.2 Hz,
1H), 4.46 (d, J = 11.0 Hz, 1H), 4.38 (dt, J = 11.8, 7.2 Hz, 1H), 4.23 (t,
J = 7.3 Hz, 1H), 4.18 (d, J = 9.8 Hz, 1H), 3.89–3.77 (m, 4H), 3.78–
3.65 (m, 5H), 3.60 (dt, J = 17.5, 9.1 Hz, 2H), 2.53 (dd, J = 21.3,
9.8 Hz, 1H), 2.30–2.14 (m, 1H), 2.05 (td, J = 11.9, 9.2 Hz, 1H), 1.76
(dd, J = 11.4, 7.6 Hz, 1H), 1.34 (d, J = 6.0 Hz, 3H), 1.15 (d, J = 6.1 Hz,
2H), 0.92–0.72 (m, 1H); 13C NMR (150 MHz, CDCl3): d 147.6, 145.8,
138.2(3), 138.1, 138.0(2), 129.1, 128.8, 128.6, 128.4, 128.2, 128.1,
127.9, 127.7, 127.6, 127.5, 116.9, 116.2, 112.8, 85.7, 83.5, 77.6,
77.5, 75.4, 75.2, 75.0, 74.5, 74.1, 73.6, 73.6, 73.5, 73.2, 73.0,
69.5(2), 69.3, 63.9, 60.0, 52.5, 51.0, 33.8, 33.6, 22.1, 19.6; ESI-HRMS:
m/z calcd for C36H39NNaO4 [M+Na]+: 572.2777, found 572.2798.
3H); 13C NMR (150 MHz, CDCl3):
d 138.1, 137.6, 128.4(2),
128.3(2), 128.1, 127.9(2), 127.8, 127.7, 127.6(2), 79.9, 77.6, 73.5,
73.4, 73.2, 72.3, 69.8, 67.6, 62.0, 61.2, 59.4, 57.5, 37.5, 21.6; ESI-
HRMS: m/z calcd for C32H40NO5 [M+H]+: 518.2906, found 518.2918.
3.7. (2R,3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-2-methyl-1-octyl-octahydropyrano[3,2-b]pyrrole (6d)
Yield: 64.4 mg, 0.11 mmol, 55%. Light red syrup: ½a D20
ꢁ
+38.1 (c
0.6, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.44–7.18 (m, 15H), 4.88
(d, J = 11.4 Hz, 1H), 4.84 (d, J = 11.4 Hz, 1H), 4.71 (t, J = 10.0 Hz,
1H), 4.58–4.53 (m, 1H), 4.48 (dt, J = 15.5, 8.8 Hz, 2H), 4.39 (q,
J = 7.5 Hz, 1H), 3.83 (dd, J = 7.9, 3.5 Hz, 1H), 3.69 (t, J = 7.7 Hz, 1H),
3.65–3.57 (m, 3H), 2.84 (t, J = 6.9 Hz, 1H), 2.72–2.60 (m, 3H),
2.13–2.04 (m, 1H), 1.61 (dd, J = 21.3, 9.4 Hz, 1H), 1.48–1.37 (m,
2H), 1.27 (dd, J = 12.6, 5.8 Hz, 2H), 1.20 (s, 8H), 1.13 (d, J = 6.0 Hz,
3H), 0.86 (dt, J = 11.1, 6.9 Hz, 3H); 13C NMR (150 MHz, CDCl3): d
139.0, 138.3(2), 128.3(2), 128.0, 127.9, 127.8, 127.6(2), 127.4,
84.0, 77.9, 74.3, 74.2, 73.9, 73.8, 73.4, 70.0, 67.2, 56.8, 53.3, 37.8,
31.9, 29.6, 29.4, 27.7, 26.4, 22.7, 21.2, 14.11; ESI-HRMS: m/z calcd
for C38H52NO4 [M+H]+: 586.3896, found 586.3916.
3.11. (3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-2-methyl-1-(4-methylphenyl)octahydropyrano[3,2-
b]pyrrole (6h)
Yield: 85.6 mg, 0.152 mmol, 76%, major:minor = 1:1. Light red
syrup: ½a 2D0
ꢁ
+34.7 (c 0.4, CHCl3); 1H NMR (600 MHz, CDCl3): d
7.36–7.21 (m, 21H), 7.17 (dd, J = 15.1, 7.2 Hz, 5H), 7.10–7.06 (m,
2H), 7.02 (d, J = 8.2 Hz, 2H), 6.93 (d, J = 8.0 Hz, 2H), 6.87 (t,
J = 8.8 Hz, 4H), 6.74 (d, J = 8.2 Hz, 2H), 4.86 (d, J = 10.8 Hz, 1H),
4.74 (t, J = 7.9 Hz, 2H), 4.71–4.65 (m, 2H), 4.60 (d, J = 12.2 Hz,
2H), 4.55 (d, J = 11.7 Hz, 3H), 4.51 (d, J = 10.1 Hz, 1H), 4.45 (d,
J = 10.9 Hz, 1H), 4.36 (dt, J = 13.9, 7.0 Hz, 1H), 4.19 (t, J = 7.3 Hz,
1H), 4.15 (d, J = 10.3 Hz, 2H), 3.80 (dd, J = 16.4, 8.8 Hz, 4H), 3.70
(ddd, J = 29.3, 15.9, 9.2 Hz, 6H), 3.59 (dt, J = 17.1, 9.0 Hz, 2H), 2.50
(dd, J = 21.0, 9.8 Hz, 1H), 2.26 (s, 3H), 2.24–2.18 (m, 3H), 2.09–
1.99 (m, 1H), 1.79–1.72 (m, 1H), 1.33 (d, J = 5.9 Hz, 3H), 1.26 (s,
3H), 1.13 (d, J = 6.0 Hz, 2H), 0.87 (dd, J = 18.4, 11.0 Hz, 1H); 13C
NMR (150 MHz, CDCl3): d 145.6, 143.5, 138.3, 138.2, 138.1(2),
138.0, 128.6, 128.4, 128.3, 128.2, 128.0, 127.9(2), 127.8, 127.7(2),
127.6(2), 127.5, 126.1, 116.7, 112.9, 85.8, 83.2, 77.6, 77.5, 75.3,
75.1, 74.9, 74.4, 74.1, 73.6, 73.6, 73.1, 73.0, 69.6, 69.3, 64.4, 60.5,
52.7, 51.0, 33.9, 29.7, 22.1, 20.4, 20.2, 19.7; ESI-HRMS: m/z calcd
3.8. (2R,3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-1-hexyl-2-methyl-octahydropyrano[3,2-b]pyrrole (6e)
Yield: 70.2 mg, 0.126 mmol, 63%. Light red syrup: ½a D20
ꢁ
+42.6 (c
0.4, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.39–7.22 (m, 15H), 4.88
(d, J = 11.3 Hz, 1H), 4.83 (d, J = 11.4 Hz, 1H), 4.72 (d, J = 11.0 Hz,
1H), 4.56 (d, J = 12.2 Hz, 1H), 4.47 (dd, J = 16.4, 11.9 Hz, 2H), 4.39
(dd, J = 14.6, 7.4 Hz, 1H), 3.85–3.80 (m, 1H), 3.69 (t, J = 7.3 Hz, 1H),
3.66–3.56 (m, 3H), 2.84 (t, J = 6.6 Hz, 1H), 2.73–2.59 (m, 3H),
2.13–2.04 (m, 1H), 1.73 (s, 1H), 1.61 (dd, J = 20.4, 9.7 Hz, 1H),
1.48–1.37 (m, 2H), 1.28–1.06 (m, 8H), 0.84 (t, J = 6.9 Hz, 3H); 13C
NMR (150 MHz, CDCl3): d 138.9, 138.3(2), 128.3(2), 128.0, 127.9,
127.8, 127.7, 127.6, 127.4, 84.0, 77.9, 74.3, 74.2, 73.9, 73.8, 73.4,
70.0, 67.2, 56.8, 53.3, 37.8, 31.9, 27.3, 26.3, 22.7, 21.1, 14.1; ESI-
HRMS: m/z calcd for C36H48NO4 [M+H]+: 558.3583, found 558.3593.
C
37H42NO4 [M+H]+: 564.3114, found 564.3113.
3.12. (2R,3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-2-methyl-1-(o-tolyl)-octahydropyrano[3,2-b]pyrrole
(6i)
3.9. (2R,3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-
[(benzyloxy)methyl]-1-[2-(4-fluorophenyl)ethyl]-2-methyl-
octahydropyrano[3,2-b]pyrrole (6f)
Yield: 65.3 mg, 0.116 mmol, 58%. Light red syrup: ½a D20
ꢁ
+33.4 (c
Yield: 70.2 mg, 0.118 mmol, 59%. Light red syrup: ½a D20
ꢁ
+34.7 (c
0.2, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.32 (d, J = 19.6 Hz, 5H),
7.29–7.20 (m, 7H), 7.19–7.10 (m, 4H), 7.06 (dd, J = 6.9, 2.3 Hz,
2H), 6.80 (dd, J = 7.3, 1.7 Hz, 1H), 4.69 (dd, J = 12.3, 7.6 Hz, 1H),
4.58 (d, J = 12.3 Hz, 1H), 4.49 (d, J = 12.2 Hz, 1H), 4.34 (d,
J = 11.4 Hz, 1H), 4.27 (d, J = 11.0 Hz, 1H), 4.20 (d, J = 11.4 Hz, 1H),
4.13 (d, J = 11.0 Hz, 1H), 4.07 (ddd, J = 9.1, 5.2, 2.4 Hz, 1H), 3.65
(dd, J = 10.5, 2.4 Hz, 1H), 3.63–3.58 (m, 2H), 3.54 (dd, J = 5.9,
4.0 Hz, 1H), 3.45 (dd, J = 6.8, 4.0 Hz, 1H), 3.01–2.89 (m, 1H), 2.53–
2.42 (m, 1H), 2.32 (s, 3H), 1.73–1.63 (m, 1H), 0.96 (d, J = 6.0 Hz,
3H); 13C NMR (150 MHz, CDCl3): d 147.6, 139.2, 138.5, 138.3,
138.1, 130.8, 128.3, 128.2, 128.1, 127.8, 127.7, 127.5, 126.8,
125.7, 124.5, 80.0, 77.7(2), 73.3, 72.7(2), 72.2, 70.4, 69.4, 62.1,
40.3, 18.7, 18.5; ESI-HRMS: m/z calcd for C37H41NNaO4 [M+Na]+:
586.2933, found 586.2946.
0.4, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.35–7.23 (m, 13H), 7.19–
7.13 (m, 2H), 6.92 (dd, J = 8.2, 5.7 Hz, 2H), 6.85 (t, J = 8.7 Hz, 2H),
4.95 (d, J = 11.5 Hz, 1H), 4.78 (d, J = 11.6 Hz, 1H), 4.73 (t,
J = 7.8 Hz, 1H), 4.57 (d, J = 12.2 Hz, 1H), 4.48 (d, J = 10.9 Hz, 2H),
4.43 (dd, J = 14.8, 7.5 Hz, 1H), 3.87–3.82 (m, 1H), 3.76–3.71 (m,
1H), 3.67–3.58 (m, 3H), 3.00–2.86 (m, 3H), 2.83–2.73 (m, 1H),
2.72–2.61 (m, 2H), 2.15 (dt, J = 13.2, 6.6 Hz, 1H), 1.69–1.57 (m,
1H), 1.17 (d, J = 6.0 Hz, 3H); 13C NMR (150 MHz, CDCl3): d 162.0,
160.4, 138.8, 138.3, 138.2, 136.2, 130.0(2), 128.4, 128.0, 127.8,
127.7, 127.6, 127.5, 115.1, 114.9, 83.9, 77.9, 74.3(2), 74.2, 73.8,
73.4, 70.0, 66.9, 56.6, 54.3, 38.0, 31.7, 20.7; ESI-HRMS: m/z calcd
for C38H43FNO4 [M+H]+: 596.3176, found 596.3171.
3.10. (3aR,5R,6S,7R,7aS)-6,7-bis(benzyloxy)-5-[(benzyloxy)-
methyl]-2-methyl-1-phenyl-octahydropyrano[3,2-b]pyrrole
(6g)
3.13. (3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-1-butyl-octahydropyrano[3,2-b]pyrrole (6j)
Yield: 70.3 mg, 0.128 mmol, 64%, major:minor = 3:2. Red syrup:
Yield: 55.7 mg, 0.110 mmol, 55%. Light red syrup: ½a D20
ꢁ
+24.1 (c
½
a 2D0
ꢁ
ꢂ19.2 (c 0.6, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.38–7.15 (m,
0.5, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.36–7.17 (m, 15H), 4.88
(d, J = 10.4 Hz, 1H), 4.81–4.67 (m, 2H), 4.63–4.37 (m, 5H), 3.91–
28H), 7.12 (t, J = 7.9 Hz, 2H), 7.10–7.07 (m, 2H), 6.94 (d, J = 8.3 Hz,

X. Ma et al. / Carbohydrate Research 366 (2013) 55–62
61
3.83 (m, 1H), 3.68 (s, 1H), 3.59 (d, J = 3.2 Hz, 2H), 3.19 (s, 1H), 2.92
(s, 1H), 2.58 (s, 1H), 2.28 (s, 1H), 2.11 (s, 2H), 1.90 (s, 1H), 1.49 (s,
2H), 1.31–1.20 (m, 2H), 0.86 (t, J = 7.4 Hz, 3H); 13C NMR (150 MHz,
CDCl3): d 138.6, 128.3(2), 128.4(2), 127.9, 127.8, 127.7, 127.6, 77.7,
74.6, 73.8, 73.3, 70.2, 68.5, 55.6, 51.5, 30.1, 29.7, 20.7, 14.0; ESI-
127.6(2), 115.1, 115.0, 77.7, 74.9, 74.5, 74.0(2), 73.3, 70.2, 68.2,
57.2, 51.5, 33.7, 30.1, 29.7; ESI-HRMS: m/z calcd for C37H41FNO4
[M+H]+: 582.3020, found 582.3014.
3.18. (3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-1-(p-tolyl)-octahydropyrano[3,2-b]pyrrole (6o)
HRMS: m/z calcd for
C
33H42NO4 [M+H]+: 516.3114, found
516.3108.
Yield: 68.1 mg, 0.124 mmol, 62%. Red syrup: ½a D20
ꢂ19.8 (c 1.2,
ꢁ
3.14. (3aR,5R,6S,7R,7aS)- 6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]- 1-hydroxyethyl-octahydropyrano[3,2-b]pyrrole (6k)
CHCl3); 1H NMR (600 MHz, CDCl3): d 7.38–6.98 (m, 19H), 4.79 (d,
J = 11.0 Hz, 1H), 4.62 (d, J = 10.4 Hz, 1H), 4.58 (t, J = 8.8 Hz, 2H),
4.52 (d, J = 4.0 Hz, 1H), 4.50 (s, 1H), 3.93 (s, 1H), 3.83 (d,
J = 9.0 Hz, 2H), 3.71–3.63 (m, 3H), 3.28 (d, J = 8.4 Hz, 1H), 2.41–
2.29 (m, 2H), 2.26 (s, 3H), 2.10 (s, 1H), 1.57 (s, 1H); 13C NMR
(150 MHz, CDCl3): d 138.1, 138.0(2), 129.9, 129.8, 129.7, 128.6,
128.4(2), 128.2, 128.1, 128.0, 127.8, 127.7, 127.5, 74.9, 74.8,
74.7(2), 74.4, 73.5, 69.7, 69.6, 63.8, 29.7, 20.5, 20.4; ESI-HRMS:
m/z calcd for C36H39NNaO4 [M+Na]+: 572.2777, found 572.2771.
Yield: 64.4 mg, 0.128 mmol, 64%. Colourless syrup: ½a D20
ꢁ
+22.3 (c
0.9, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.35–7.18 (m, 15H), 4.70
(d, J = 11.7 Hz, 1H), 4.64–4.55 (m, 3H), 4.49 (d, J = 12.2 Hz, 1H),
4.47–4.44 (m, 1H), 4.40–4.36 (m, 1H), 3.91 (dt, J = 8.1, 4.2 Hz,
1H), 3.79 (s, 1H), 3.67–3.61 (m, 1H), 3.59 (dd, J = 7.7, 4.9 Hz, 1H),
3.55–3.49 (m, 3H), 3.37 (s, 1H), 2.99 (t, J = 9.8 Hz, 1H), 2.82–2.73
(m, 1H), 2.46 (d, J = 12.7 Hz, 1H), 2.21 (dd, J = 17.6, 8.5 Hz, 1H),
2.15 (dtd, J = 11.0, 7.8, 3.0 Hz, 1H), 1.99–1.91 (m, 1H); 13C NMR
(150 MHz, CDCl3): d 138.3, 138.2, 137.7, 129.7, 128.5(2), 128.4,
128.3(2), 127.9(2), 127.8, 127.6, 77.6, 76.3, 75.6, 74.3, 73.3, 72.9,
72.8, 72.7, 70.2, 59.7, 57.2, 52.7, 30.0; ESI-HRMS: m/z calcd for
3.19. (3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-1-(2-methoxy-phenethyl)-octahydropyrano[3,2-
b]pyrrole (6p)
C
31H38NO5 [M+H]+: 504.2750, found 504.2744.
Yield: 79.5 mg, 0.134 mmol, 67%. Light red syrup: ½a D20
ꢁ
+14.3 (c
0.5, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.41–6.67 (m, 19H), 4.82
(d, J = 11.0 Hz, 1H), 4.71 (d, J = 11.3 Hz, 1H), 4.53 (d, J = 12.1 Hz,
2H), 4.46 (d, J = 11.2 Hz, 2H), 3.87 (dt, J = 7.7, 3.7 Hz, 1H), 3.84–
3.76 (m, 1H), 3.72–3.63 (m, 4H), 3.63–3.55 (m, 2H), 3.32 (s, 1H),
3.20 (s, 1H), 2.85 (s, 2H), 2.65 (s, 1H), 2.56 (s, 1H), 2.30 (s, 1H),
2.12 (s, 1H), 1.93 (s, 1H), 1.78 (s, 1H); 13C NMR (150 MHz, CDCl3):
d 157.5, 138.6, 138.3, 130.3, 129.7, 128.4, 128.3, 127.9, 127.8,
127.7(2), 127.6, 127.5, 127.3, 120.4, 110.2, 77.6, 74.7, 73.9, 73.3,
70.1, 68.3, 55.7, 55.1, 51.3, 30.1, 29.1; ESI-HRMS: m/z calcd for
3.15. (3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-1-octyl-octahydropyrano[3,2-b]pyrrole (6l)
Yield: 48.0 mg, 0.084 mmol, 42%. Light red syrup: ½a D20
ꢁ
+20.2 (c
0.4, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.38–7.17 (m, 15H), 4.87
(s, 1H), 4.70 (d, J = 18.9 Hz, 3H), 4.50 (dd, J = 32.4, 11.4 Hz, 4H),
3.89–3.84 (m, 1H), 3.67 (s, 1H), 3.58 (d, J = 2.7 Hz, 2H), 3.16 (s,
1H), 2.88 (s, 1H), 2.56 (s, 1H), 2.26 (s, 1H), 2.10 (s, 1H), 1.83 (d,
J = 36.8 Hz, 1H), 1.49 (s, 1H), 1.26 (dd, J = 24.0, 14.9 Hz, 12H), 0.87
(t, J = 7.1 Hz, 3H); 13C NMR (150 MHz, CDCl3): d 141.0, 138.6,
138.2, 128.9, 128.6, 128.4, 127.9, 127.7, 127.6, 127.0, 77.6, 74.5,
73.8, 73.3, 70.1, 68.4, 65.3, 55.8, 51.5, 31.8, 29.3, 27.5, 22.6, 14.1;
ESI-HRMS: m/z calcd for C37H50NO4 [M+H]+: 572.3740, found
572.3734.
C
38H44NO5 [M+H]+: 584.3219, found 584.3214.
Acknowledgment
We are grateful for financial support from the Chinese Academy
of Sciences (Hundreds of Talents Program) and the National Natu-
ral Science Foundation of China (20972151).
3.16. (3aR,5R,6S,7R,7aS)-6,7-Bis(benzyloxy)-5-[(benzyloxy)-
methyl]-1-hexyl-octahydropyrano[3,2-b]pyrrole (6m)
Supplementary data
Yield: 58.7 mg, 0.108 mmol, 54%. Light red syrup: ½a D20
ꢁ
+20.8 (c
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.carres.2012.
11.016.
0.6, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.41–7.21 (m, 15H), 4.92
(d, J = 10.4 Hz, 1H), 4.84–4.70 (m, 2H), 4.62–4.53 (m, 2H), 4.50 (t,
J = 11.7 Hz, 2H), 3.95–3.88 (m, 1H), 3.72 (d, J = 7.6 Hz, 1H), 3.63
(d, J = 2.4 Hz, 2H), 3.22 (s, 1H), 2.94 (s, 1H), 2.61 (s, 1H), 2.30 (s,
1H), 2.14 (s, 1H), 1.93 (s, 1H), 1.54 (s, 2H), 1.28 (dd, J = 20.9,
7.5 Hz, 8H), 0.89 (t, J = 7.0 Hz, 3H); 13C NMR (150 MHz, CDCl3): d
138.6, 138.3, 128.4, 127.9, 127.8, 127.7(2), 127.6, 127.5, 81.9,
77.7, 74.6, 73.8, 73.3, 70.2, 68.5, 55.8, 51.4, 31.8, 30.1, 27.9, 27.2,
22.6, 14.0; ESI-HRMS: m/z calcd for C35H46NO4 [M+H]+: 544.3427,
found 544.3421.
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ꢁ
+21.0 (c
0.7, CHCl3); 1H NMR (600 MHz, CDCl3): d 7.38–6.85 (m, 19H), 4.89
(d, J = 11.1 Hz, 1H), 4.71 (d, J = 11.3 Hz, 2H), 4.62–4.43 (m, 5H),
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2.28 (s, 1H), 2.14 (s, 1H), 1.92 (s, 1H); 13C NMR (150 MHz, CDCl3):
d 162.2, 160.6, 138.5, 138.2(2), 130.0(2), 128.4, 128.0, 127.7,

62
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