Barton radical reactions of 2-C-branched carbohydrates

Article abstract of DOI:10.1039/c1ob06370g

Barton esters have been introduced into the side chain of carbohydrates with high yields in only a few steps from easily available glycals. Their radical reactions afford 2-C-methyl and 2-C-bromomethyl hexoses, pentoses and disaccharides in good yields in

Full text of DOI:10.1039/c1ob06370g

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PAPER
Barton radical reactions of 2-C-branched carbohydrates†
Tukaram M. Pimpalpalle, Jian Yin‡ and Torsten Linker*
Received 11th August 2011, Accepted 1st September 2011
DOI: 10.1039/c1ob06370g
Barton esters have been introduced into the side chain of carbohydrates with high yields in only a few
steps from easily available glycals. Their radical reactions afford 2-C-methyl and 2-C-bromomethyl
hexoses, pentoses and disaccharides in good yields in analytically pure form. Since the Barton esters
have been synthesized by an oxidative radical addition and their transformations by reductive radical
processes, our results demonstrate the power of such reactions in carbohydrate chemistry.
acids (KDO),5 to generate radicals at the anomeric center6 or
Introduction
with carbohydrates as chiral auxiliaries.7 Herein we describe the
first Barton reactions of 2-C-branched saccharides, which allow
the reduction and further functionalization of the side-chain of
carbohydrates.
Radical reactions are of current interest in organic synthesis and
have found many applications in natural product synthesis, and
particularly in carbohydrate chemistry.1 Although the generation
of radicals from alkyl halides in the presence of tin hydrides1 or
silanes2 is still the most common procedure, carboxylic acids 1 can
serve as radical precursors as well. For instance, electrochemical
oxidation of the corresponding carboxylates 2 (Kolbe electrolysis)
provides alkyl radicals 3 after decarboxylation,3 and the same
radicals 3 are also obtained by photolysis of thiohydroxamate
esters 4 under cleavage of N–O and C–C bonds under mild
conditions (Barton reaction) (Scheme 1).4
Results and discussion
During our studies on transition-metal-mediated radical reactions
in carbohydrate chemistry,8 we developed an easy entry to
carboxylic acids 1a.9 For the synthesis of the corresponding Barton
esters 4a, the reaction conditions had to be carefully optimized
(Table 1). Thus, thionyl or oxalyl chloride, which are often used
in the preparation of Barton esters4 via the acid chlorides and 2-
mercaptopyridine-N-oxide sodium salt (R = Na) failed (entries
1 and 2). The starting material gluco-1a decomposed even at
0 ◦C, due to the acidic reaction conditions. Next, we investigated
N,N¢-dicyclohexyl-carbodiimide (DCC) in combination with the
Table 1 Synthesis of Barton esters 4a from carboxylic acids 1aa
Scheme 1 Generation of radicals 3 from carboxylic acids 1.
Entry
Config.
Activator
R
Conv. (%)
4a (%)b
Although there are numerous examples of tin hydride radical
reactions in carbohydrate chemistry,1 the Barton reaction was only
applied in this field in the total synthesis of keto-deoxy-octulosonic
1
2
3
4
5
6
7
8
9
gluco
gluco
gluco
gluco
galacto
xylo
arabino
malto
lacto
SOCl2
(COCl)2
DCC
EDCI
EDCI
EDCI
EDCI
EDCI
EDCI
Na
Na
H
H
H
H
H
H
H
> 97
> 97
70
> 97
> 97
> 97
> 97
> 97
> 97
< 5c
< 5c
65
90
93
91
89
81
83
Department of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-
25, 14476 Potsdam, Germany. E-mail: linker@uni-potsdam.de; Fax: +49
331 9775076; Tel: +49 331 9775212
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c1ob06370g
a For procedure see experimental section. b Yield of analytically pure
products, isolated by column chromatography. c Decomposition of starting
material 1a.
‡ Current address: Department of Biomolecular Systems, Max Planck
Institute of Colloids and Interfaces, Am Mu¨hlenberg 1, 14776 Potsdam &
Freie Universita¨t Berlin Institut fu¨r Chemie und Biochemie, Arnimallee
22, 14195 Berlin, Germany
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Table 2 Reduction of Barton esters 4a to 2-C-methyl glycosides 5a
Table 3 Radical bromination of Barton esters 4a to bromides 6a
Entry Config.
Temp. (◦C)
Light source Conv. (%)
5 (%)b
Entry Config.
Temp. (◦C)
Light Source
Conv. (%)
6 (%)b
1
2
3
4
5
6
7
8
9
gluco
gluco
gluco
gluco
galacto
xylo
arabino
malto
lacto
80
25
25
25
25
25
25
25
25
—
> 97
< 5
70
> 97
> 97
> 97
> 97
> 97
> 97
30c
< 5
56
78
79
77
71
68
64
1
2
3
4
5
6
gluco
galacto
xylo
arabino
malto
lacto
25
25
25
25
25
25
Hg lamp
Hg lamp
Hg lamp
Hg lamp
Hg lamp
Hg lamp
>97
>97
>97
>97
>97
>97
76
74
71
73
70
69
Na lamp
W lamp
Hg lamp
Hg lamp
Hg lamp
Hg lamp
Hg lamp
Hg lamp
a For procedure see experimental section. b Yield of analytically pure
products, isolated by column chromatography.
a For procedure see experimental section. b Yield of analytically pure
products, isolated by column chromatography. c Decomposition of starting
material 4a.
such transformations in carbohydrate chemistry. Thus, we found
a new entry to 2-C-methyl saccharides, which are available by
cyclopropane-opening only as anomeric mixtures.13
free 2-mercaptopyridine-N-oxide (R = H), which has been used
recently for the synthesis of Barton esters.10 Although incomplete
conversion was observed, the product gluco-4a was isolated with
65% yield (entry 3).
To introduce functional groups by the Barton reaction, the
decarboxylative halogenation is an attractive choice, since long
radical chains and mild conditions are advantageous.4 Again, we
employed a 250 W low-pressure mercury lamp for initiation, this
time in the presence of bromotrichloromethane as a cheap bromine
source (Table 3). Indeed, the 2-C-bromomethyl glycosides 6 were
isolated with moderate to good yields with gluco-, galacto-, xylo-,
arabino-, malto- and lacto-configurations. Although similar com-
pounds are available by cyclopropane-opening,13a,14 our method is
applicable for various saccharides and provides sole diastereomers
and no anomeric mixtures. Furthermore, the bromides 6 might
serve as precursors for SN2 or radical reactions in carbohydrate
chemistry.
The best conditions were finally found with N-(3-
dimethylaminopropyl)-N¢-ethylcarbodiimide (EDCI) as activator
for the acid group.11 Thus, Barton ester gluco-4a was isolated
in 90% yield (entry 4). We were able to successfully apply these
conditions for other hexoses, pentoses and even disaccharides
(Table 1, entries 5–9). Although Barton esters are quite sensitive
compounds, all products 4a were isolated in good to high yields
in analytically pure form, including correct elemental analysis
(experimental section). Accordingly, we found a convenient entry
to such radical precursors in only a few steps from easily available
glycals.
Conclusions
To establish the potential of Barton esters 4a in the synthesis
of 2-C-branched saccharides, we first investigated reductive decar-
boxylations (Table 2). This is a very common transformation in
radical chemistry, and it requires only t-butanethiol as hydrogen
atom donor and no toxic tin hydrides.4 However, due to the
lability of carbohydrates, the conditions for the initiation had to
be carefully optimized with Barton ester gluco-4a. Thus, simple
thermolysis in benzene afforded the 2-C-methyl glycoside gluco-
5 with only 30% yield besides decomposition of the starting
material (entry 1). Therefore, we investigated the initiation of
the Barton reaction by photolysis, which is attractive in terms
of lower temperatures and milder conditions.4c However, sodium
lamp irradiation gave no conversion (entry 2). With a tungsten
lamp, which was used in natural product synthesis via Barton
esters very recently,12 the yield was increased to 56% (entry 3).
Finally, the best results were obtained with a 250 W low-pressure
mercury lamp, which afforded 2-C-methyl glycoside gluco-5 with
78% yield (entry 4). We were again able to apply these conditions
for other hexoses, pentoses and disaccharides (Table 2, entries 5–
9) and all products 5 were isolated with moderate to good yields
in analytically pure form (experimental section). Interestingly, our
synthetic approach is based on a combination of oxidative (CAN-
mediated addition of malonates to glycals) and reductive (Barton
decarboxylation) radical reactions, demonstrating the power of
In conclusion, we have synthesized Barton esters of 2-C-branched
carbohydrates for the first time. The method is applicable for
hexoses, pentoses and disaccharides and affords analytically pure
products with high yields. The Barton esters are suitable precursors
for radical reductions and brominations. Thus, 2-C-methyl and
2-C-bromomethyl saccharides are easily available. Our studies
demonstrate the power of radical reactions in carbohydrate
chemistry, since products were obtained by a sequence of oxidative
malonate additions and reductive decarboxylations. The bromide
groups of the 2-C-branched saccharides are suitable precursors for
further transformations, which are currently under investigation
in our lab.
Experimental section
General methods
All reactions requiring anhydrous conditions were performed
under a positive pressure of argon using oven-dried glassware
(110 ◦C), which was cooled under argon. Solvents for anhydrous
reactions were dried according to Perrin et al.15 Benzene and
dichloromethane were distilled from calcium hydride and stored
over molecular sieves. All commercial reagents were obtained
104 | Org. Biomol. Chem., 2012, 10, 103–109
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from Sigma-Aldrich, Acros or Fluka Chemical Co. Progress of
the reactions was monitored by tlc. Column chromatographies
were performed on silica gel 60–120/100–200/230–400 mesh
obtained from ACROS Organics Belgium. Typical syringe and
cannula techniques were used to transfer air- and moisture-
sensitive reagents. IR spectra were recorded on a Perkin–Elmer
infrared spectrometer model 599-B and model 1620 FT-IR. NMR
spectra were recorded either on a Bruker Avance 300 or Avance 500
or Avance 600 instrument using deuterated chloroform solvent.
Elemental analyses were performed on a Vario EL III analyzer
(Elementar Analysensysteme GmbH, Hanau, Germany). Optical
rotations were measured on a JASCO P-1020 digital polarimeter
at 589 nm, melting points on an Electrothermal MEL-TEMP
apparatus (uncorrected).
2.85 (dd, J = 14.6, 6.0 1H 7¢-H), 3.40 (s, 3H, OMe), 3.46 (dd,
J = 10.8, 2.2, Hz, 1H, 3-H), 3.53 (dd, J = 6.9, 5.8 Hz, 1H, 6-H),
3.56 (ddd, J = 8.8, 5.8, 0 Hz, 1H, 5-H), 3.63 (dd, J = 8.8, 6.9 Hz,
1H, 6¢-H), 3.93 (d, J = 2.2 Hz, 1H, 4-H), 4.26 (d, J = 8.5 Hz, 1H
1-H), 4.35 (d, J = 11.1 Hz, 1H, CH2Ph), 4.39 (d, J = 11.7 Hz,
1H, CH2Ph), 4.43(d, J = 11.6 Hz, 1H, CH2Ph), 4.55 (d, J = 11.7
Hz, 1H, CH2Ph), 4.65 (d, J = 11.1 Hz, 1H, CH2Ph), 4.81 (d, J =
11.6 Hz, 1H, CH2Ph), 6.28 (dt, J = 6.8, 1.6 Hz 1H thiopyr. C-H),
7.01 (dd, J = 6.8, 1.5 Hz 1H thiopyr. C-H), 7.03 (dt, J = 6.8, 1.5
Hz 1H thiopyr. C-H), 7.15–7.21 (m, 15H, arom. H), 7.55 (dd, J =
6.8, 1.6 Hz, 1H thiopyr. C-H);13C NMR (150 MHz, CDCl3): d =
30.30 (t, C-7), 40.1 (d, C-2), 56.7 (q, OMe), 68.7 (t, C-6), 70.6,
73.5, 80.6 (3d, C-3, C-4, C-5), 71.5, 73.6, 74.4 (3t, CH2Ph), 103.5
(C-1), 112.1 (d, thiopyr. N-C-H), 127.5, 127.8, 127.9, 128.0, 128.1,
128.2 (15d, arom. C-H), 133.3, 137.1, 137.7 (3d, thiopyr. C-H),
137.2, 137.8, 138.5 (3 s, arom. C-CH2O), 167.5 (s, COOR), 175.9
(NC S); Elemental analysis(%) calcd for C35H37NO7S: C 68.27,
H 6.06, N 2.27, S 5.21; found: C 68.23, H 6.03, N 2.29, S 5.29;
Mass (ESI-MS); m/z 638.44(M + Na)+.
General procedure for the synthesis of Barton esters 4a
The sugar carboxylic acid 1a (2.0 mmol) was dissolved in
30 mL of dry dichloromethane and was protected from
light with an aluminium foil at 0 ◦C. 2-Mercaptopyridine
N-oxide (390 mg, 2.5 mmol), N-(3-dimethylaminopropyl)-N-
ethylcarbodiimide (EDCI) (620 mg, 4.0 mmol) and a catalytic
amount of 4-(dimethylamino)pyridine (DMAP) (20 mg) were
added and the mixture was stirred at 0 ◦C for 1–2 h until tlc showed
complete conversion of the starting material. Then a saturated
solution of sodium bicarbonate was added, and the mixture was
extracted with dichloromethane (3 ¥ 10 mL). The combined
organic extracts were dried using sodium sulfate, filtered and
concentrated under reduced pressure at 30 ◦C. The desired product
was isolated by flash chromatography in analytically pure form.
xylo-4a. 900 mg (91%) of a pale yellow syrup; Rf 0.44
(hexane/ethyl acetate 2 : 1); [a]2D0 = +32.7 (c = 1.01 in CHCl3); IR
(film): v = 3063, 3030, 2924, 1812, 1722, 1607, 1496, 1465, 1374,
1
1205, 1157, 1069, 1028, 995 cm-1; H NMR (600 MHz, CDCl3):
d = 2.18 (dddd, J = 10.8, 8.3, 6.8, 5.3 Hz 1H, 2-H), 2.75 (dd, J =
15.5, 6.8 Hz 1H, 6-H), 2.85 (dd, J = 15.5, 5.3 Hz, 1H, 6¢-H), 3.21
(dd, J = 11.7, 9.4 Hz, 1H 5-H), 3.40 (s, 3H, OMe), 3.47 (dd, J =
10.8, 8.2, Hz, 1H, 3-H), 3.62 (ddd, J = 9.4, 8.2, 5.0 Hz, 1H, 4-H),
3.98 (dd, J = 11.7, 5.0 Hz, 1H, 5¢-H), 4.23 (d, J = 8.3 Hz, 1H,
1-H), 4.56 (d, J = 10.9 Hz, 1H, CH2Ph) 4.57 (d, J = 11.7 Hz, 1H,
CH2Ph), 4.61 (d, J = 11.7 Hz, 1H, CH2Ph), 4.96 (d, J = 10.9 Hz,
1H, CH2Ph), 6.24 (dt, J = 6.8, 1.8 Hz 1H thiopyr. C-H), 6.90 (dd,
J = 6.8, 1.8, Hz 1H thiopyr. C-H), 7.03 (dt, J = 6.8, 1.8 Hz 1H
thiopyr. C-H), 7.21–7.28 (m, 10H, arom. H), 7.55 (dd, J = 6.8, 1.8
Hz, 1H thiopyr. C-H); 13C NMR (150 MHz, CDCl3): d = 30.8 (t,
C-6), 43.8 (d, C-2), 56.8 (q, OMe), 63.5 (t, C-5), 72.7, 74.6, (2t,
CH2Ph), 79.5, 80.5 (2d, C-3, C-4), 103.4 (d, C-1), 112.0 (d, thiopyr.
N-C-H), 127.8, 127.8, 127.9, 128.3, 128.5, 128.5 (10d, arom. C-H),
133.4, 137.1, 137.7 (3d, thiopyr. C-H), 137.8, 138.1, (2 s, arom. C-
CH2O), 167.4 (s, COOR), 175.8 (NC S); Elemental analysis(%)
calcd for C27H29NO6S: C 65.44, H 5.90, N 2.83, S 6.47; found C
65.39, H 5.93, N 2.86, S 6.43; Mass (ESI-MS); m/z 518.24(M +
Na)+.
gluco-4a. 1.10 g (90%) of a pale yellow syrup; Rf 0.42
(hexane/ethyl acetate 2 : 1); [a]2D0 = +25.6 (c = 1.02 in CHCl3); IR
(film): v = 2925, 1806, 1607, 1525, 1446, 1410, 1362, 1281, 1207,
1050 cm-1; 1H NMR (500 MHz, CDCl3): d = 2.26 (ddt, J = 11.0,
8.7, 6.0 Hz, 1H, 2-H), 2.77 (d, J = 6.0 Hz, 2H, 7-H), 3.40 (dt, J =
9.3, 5.2 Hz, 1H, 5-H), 3.42 (s, 3H, OMe), 3.50 (dd, J = 11.0, 8.8,
Hz, 1H, 3-H), 3.64 (dd, J = 9.3, 8.8 Hz, 1H, 4-H), 3.68 (d, J =
5.2 Hz, 2H, 6-H), 4.25 (d, J = 8.7 Hz, 1H, 1-H), 4.47 (d, J = 11.9
Hz, 1H, CH2Ph), 4.52 (d, J = 10.9 Hz, 1H, CH2Ph), 4.57 (d, J =
11.9 Hz, 1H, CH2Ph), 4.58 (d, J = 11.9 Hz, 1H CH2Ph), 4.71 (d,
J = 11.0, Hz, 1H, CH2Ph), 4.91 (d, J = 11.0 Hz, 1H, CH2Ph), 6.24
(dt, J = 7.0, 1.5 Hz 1H thiopyr. C-H), 6.96 (dt, J = 7.0, 1.5 Hz 1H
thiopyr. C-H), 7.00 (dd, J = 7.0, 1.5 Hz 1H thiopyr. C-H), 7.06-7.28
(m, 15H, arom. H), 7.51 (dd, J = 7.0, 1.5 Hz, 1H thiopyr. C-H);
13C NMR (125 MHz, CDCl3): d = 30.2 (t, C-7), 44.7 (d, C-2), 56.8
(q, OMe), 68.4 (t, C-6), 73.3, 74.5, 74.7 (3t, CH2Ph), 74.9, 79.5,
81.8 (3d, C-3, C-4, C-5), 102.9 (d, C-1), 112.1 (d, thiopyr. N-C-H),
127.5, 127.6, 127.7, 127.9, 128.2, 128.3 (15d, arom. C-H), 133.4,
136.8, 137.5 (3d, thiopyr. C-H), 137.6, 137.7, 137.8 (3 s, arom. C-
CH2O), 167.2 (s, COOR), 175.5 (NC S); Elemental analysis(%)
calcd for C35H37NO7S: C 68.27, H 6.06, N 2.27, S 5.21; found: C
68.29, H 6.09, N 2.23, S 5.26; Mass (ESI-MS); m/z 638.41(M +
Na)+.
arabino-4a. 880 mg (89%) of a pale yellow syrup; Rf 0.44
(hexane/ethyl acetate 2 : 1); [a]2D0 = +19.7 (c = 1.01 in CHCl3); IR
(film): v = 3067, 3034, 2922, 1816, 1723, 1602, 1496, 1468, 1374,
1
1204, 1152, 1064, 1028, 995 cm-1; H NMR (600 MHz, CDCl3):
d = 2.70 (dddd, J = 11.0, 8.5, 6.6, 5.6 Hz 1H, 2-H), 2.83 (dd, J =
14.5, 5.6 Hz 1H, 6-H), 2.83 (dd, J = 14.5, 6.6 Hz, 1H, 6¢-H), 3.29
(dd, J = 12.9, 3.6, Hz, 1H 5-H), 3.43 (s, 3H, OMe), 3.50 (dd, J =
11.0, 2.8 Hz, 1H, 3-H), 3.68 (ddd, J = 3.6, 2.8, 2.1 Hz, 1H, 4-H),
4.13 (dd, J = 12.9, 2.1 Hz, 1H, 5¢-H), 4.24 (d, J = 8.5 Hz, 1H,
1-H), 4.26 (d, J = 11.3 Hz, 1H, CH2Ph), 4.49 (d, J = 11.3 Hz, 1H,
CH2Ph), 4.58 (d, J = 12.3 Hz, 1H, CH2Ph), 4.72 (d, J = 12.3 Hz,
1H, CH2Ph), 6.32 (dt, J = 6.9, 1.8 Hz 1H thiopyr. C-H), 7.03 (dt,
J = 6.9, 1.8, Hz 1H thiopyr. C-H), 7.05 (dt, J = 6.9, 1.8 Hz 1H
thiopyr. C-H), 7.19–7.27 (m, 10H, arom. H), 7.32 (dd, J = 6.9,
1.8 Hz, 1H thiopyr. C-H); 13C NMR (150 MHz, CDCl3): d = 30.3
(t, C-6), 40.3 (d, C-2), 56.8 (q, OMe), 63.5 (t, C-5), 69.3, 70.8 (2t,
galacto-4a. 1.14 g (93%) of a pale yellow syrup; Rf 0.40
(hexane/ethyl acetate 2 : 1); [a]2D0 = +17.9 (c = 1.02 in CHCl3);
IR (film): v = 2924, 1807, 1607, 1524, 1444, 1909, 1363, 1281,
1207, 1051 cm-1; 1H NMR (600 MHz, CDCl3): d = 2.72 (ddt, J =
10.8, 8.5, 6.0 Hz, 1H, 2-H), 2.76 (dd, J = 14.6, 6.0 Hz, 1H, 7-H),
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CH2Ph), 71.0, 78.7 (2d, C-3, C-4), 103.7 (d, C-1), 112.0 (d, thiopyr.
N-C-H), 127.7, 127.9, 128.3, 128.8, 128.5, 133.5 (10d, arom. C-H),
137.0, 137.4, 137.7 (3d, thiopyr. C-H), 137.7, 137.8 (2 s, arom. C-
CH2O), 167.6 (s, COOR), 176.2 (NC S); Elemental analysis(%)
calcd for C27H29NO6S: C 65.44, H 5.90, N 2.83, S 6.47; found C
65.37, H 5.99, N 2.82, S 6.44; Mass (ESI-MS); m/z 518.24(M +
Na)+.
(6t, CH2Ph), 73.0, 73.3, 75.4, 76.8, 80.0, 80.3, 82.3 (7d, C-3, C-4,
C-5, C-8, C-9, C-10, C-11), 102.6, 103.0 (2d, C-1, C-7), 112.0 (d,
thiopyr. N-C-H), 127.2, 127.3, 127.3, 127.4, 127.5, 127-5, 127.6,
127.8, 128.0, 128.1, 128.2, 128.3 (30d, arom. C-H), 137.0, 137.3,
137.8 (3d, thiopyr. C-H), 138.0, 138.3, 138.5, 138.6, 138.7, 139.0
(6 s, arom. C-CH2O), 167.4 (s, COOR), 175.8 (NC S).
General procedure for the reduction of Barton esters 4a
malto-4a. 1.70 g (81%) of a pale yellow syrup; Rf 0.42
(hexane/ethyl acetate 2 : 1); [a]2D0 = +26.2 (c = 1.02 in CHCl3);
IR (film): v = 3032, 2941, 1832, 1751, 1648, 1497, 1480, 1215, 1155
The Barton ester 4a (2.0 mmol) was dissolved in 20 mL of
dry benzene and was protected from light with aluminium foil
under argon atmosphere. tert-Butanethiol (360 mg, 4.0 mmol)
was added at 25 ◦C. The reaction mixture was subsequently
exposed to light using a 250 W low-pressure mercury lamp.
After completion of the reaction (approximately 1–2 h), the crude
reaction mixture was concentrated and the residue was purified by
flash chromatography, affording the products 5.
1
cm-1; H NMR (500 MHz, CDCl3): d = 2.42 (ddt, J = 10.9, 8.6,
6.0 Hz 1H, 2-H), 2.71 (dd, J = 15.9, 6.0 Hz 1H, 13-H), 2.85 (dd,
J = 15.9, 6.0 Hz, 1H, 13¢-H), 3.42 (dd, J = 9.5, 3.9 1H 12-H), 3.42
(ddd, J = 9.5, 3.9, 3.0, 1H, 11-H), 3.43 (s, 3H, OMe), 3.44 (dd, J =
7.9, 4.3 Hz, 1H, 6-H), 3.50 (dd J = 7.9, 2.8 Hz, 1H 6¢-H), 3.56 (dd,
J = 9.5, 3.0 Hz, 1H, 12¢-H), 3.63 (dd, J = 10.9, 8.1 Hz, 1H, 3-H),
3.70 (dd, J = 11.3, 10.8 Hz, 1H, 9-H), 3.78 (dd, J = 9.0, 4.3, 2.8 Hz,
1H, 5-H), 3.83 (dd, J = 10.8, 9.5 Hz, 1H, 10-H), 3.88 (d, J = 11.3,
3.5 Hz, 1H, 8-H), 4.06 (t, J = 9.0, 8.0 Hz, 1H, 4-H), 4.2 (d, J = 8.6
Hz, 1H, 1-H), 4.29 (d, J = 12 Hz, 1H, CH2Ph), 4.40 (d, J = 11.0
Hz, 1H, CH2Ph), 4.46 (d, J = 12.0 Hz, 1H, CH2Ph), 4.47 (d, J =
11.5 Hz, 1H, CH2Ph), 4.48 (d, J = 11.0 Hz, 1H, CH2Ph), 4.49 (d,
J = 11.2 Hz 1H CH2Ph), 4.50 (d, J = 11.2 Hz, 1H, CH2Ph), 4.52 (d,
J = 11.5, Hz, 1H, CH2Ph), 4.66 (d, J = 11.0 Hz, 1H, CH2Ph), 4.73
(d, J = 10.3 Hz, 1H, CH2Ph), 4.76 (d, J = 10.3 Hz, 1H, CH2Ph),
4.97 (d, J = 11.0 Hz, 1H, CH2Ph), 5.33 (d, J = 3.5 1H, 7-H), 6.27
(dt, J = 7.0, 1.6 Hz 1H thiopyr. C-H), 6.90 (dd, J = 7.0, 1.6, Hz 1H
thiopyr. C-H), 7.01 (dt, J = 7.0, 1.6 Hz 1H thiopyr. C-H), 7.03–
7.29 (m, 30H, arom. H), 7.53 (dd, J = 7.0, 1.6 Hz, 1H thiopyr.
C-H);13C NMR (125 MHz, CDCl3): d = 31.5 (t, C-13), 44.2 (d,
C-2), 57.7 (q, OMe), 69.3, 70.23 (2t, C-6, C-12), 72.2, 72.9, 75.9,
76.3, 78.7, 80.7 (6t, CH2Ph), 72.9, 74.2, 74.2, 74.3, 74.3, 76.0, 76.4
(7d, C-3, C-4, C-5, C-8, C-9, C-10, C-11), 98.0, 104.0 (2d, C-1,
C-7), 113.1 (d, thiopyr. N-C-H), 128.4, 128.5, 128.5, 128.6, 128.7,
128.7, 128.8, 129.2, 129.9, 129.4 (30d arom. C-H), 138.0, 138.3,
138.6 (3d, thiopyr. C-H), 138.8, 138.9, 139.3, 139.3, 139.3, 139.6
(6 s, arom. C-CH2O), 168.4 (s, COOR), 176.8 (NC S).
gluco-5. 725 mg (78%) of a colorless syrup; Rf 0.51 (hex-
ane/ethyl acetate 6 : 1); [a]D20 = +36.4 (c = 1.01 in CHCl3); IR (film):
v = 2925, 1496, 1453, 1361, 1214, 1090, 1026, 907 cm-1;1H NMR
(300 MHz, CDCl3): d = 0.97 (d, J = 6.4, Hz, 3H, CH3), 1.70 (ddq,
J = 10.6, 8.6, 6.4 Hz, 1H, 2-H), 3.16 (dd, J = 10.6, 8.7 Hz, 1H,
3-H), 3.38 (ddd, J = 9.6, 4.5, 2.4 Hz, 1H, 5-H), 3.43 (s, 3H, OMe),
3.51 (dd, J = 9.6, 8.7, Hz, 1H, 4-H), 3.67 (dd, J = 10.8, 4.5 Hz, 1H,
6-H), 3.68 (dd, J = 10.8, 2.5 Hz, 1H, 6¢-H), 3.93 (d, J = 8.6 Hz, 1H,
1-H), 4.49 (d, J = 11.6 Hz, 2H, CH2Ph), 4.57 (d, J = 11.4 Hz, 1H,
CH2Ph), 4.72 (d, J = 10.9 Hz, 1H, CH2Ph), 4.80 (d, J = 10.9 Hz,
1H, CH2Ph), 7.10–7.29 (m, 15H, arom. H); 13C NMR (75 MHz,
CDCl3): d = 12.5 (q, CH3), 42.6 (d, C-2), 56.7 (q, OMe), 69.2 (t,
C-6), 73.4, 74.7, 75.1 (3t, CH2Ph), 75.2, 79.4, 85.2 (3d, C-3, C-4,
C-5), 105.5 (d, C-1), 127.6, 127.7, 127.8, 127.8, 128.3, 128.3 (15d,
arom. C-H), 138.1, 138.2. 138.4 (3 s, arom. C-CH2O); Elemental
analysis(%); calcd for: C29H34O5 C 75.30, H 7.41,; found: C 75.33,
H 7.47; Mass (ESI-MS); m/z 485.28(M + Na)+.
galacto-5. 730 mg (79%) of a colorless syrup; Rf 0.48 (hex-
ane/ethyl acetate 6 : 1); [a]D20 = +31.4 (c = 1.02 in CHCl3); IR (film):
v = 3030, 2924, 2867, 2358, 1718, 1496, 1454, 1363, 1206, 1153,
1078, 1028 cm-1; 1H NMR (300 MHz, CDCl3): d = 0.95 (d, J = 6.6
Hz, 3H, CH3), 2.11 (ddq, J = 11.0, 8.6, 6.6 Hz, 1H, 2-H), 3.03 (d,
J = 11.0, 2.6 Hz, 1H, 3-H), 3.39 (s, 3H, OMe), 3.44 (dd, J = 7.4,
5.4 Hz, 1H, 5-H), 3.57 (dd, J = 9.2, 5.4 Hz, 1H, 6-H), 3.57 (dd, J =
9.2. 7.4 Hz, 1H, 6¢-H), 3.80 (d, J = 2.5 Hz, 1H, 4-H), 3.87 (d, J =
8.6 Hz, 1H, 1-H), 4.35 (d, J = 11.6 Hz, 1H, CH2Ph), 4.37 (d, J =
11.6 Hz, 1H, CH2Ph), 4.42 (d, J = 11.8 Hz, 1H, CH2Ph), 4.53 (d,
J = 11.7, 1H, CH2Ph), 4.62 (d, J = 11.7 Hz, 1H, CH2Ph), 4.80 (d,
J = 11.8 Hz, 1H, CH2Ph), 7.15–7.28 (m, 15H, arom. H); 13C NMR
(75 MHz, CDCl3): d = 12.3 (q, CH3), 37.3(d, C-2), 56.6 (q, OMe),
69.3 (t, C-6), 71.6, 73.5, 74.1 (3t, CH2Ph), 70.6, 73.6, 83.0 (3d,
C-3, C-4, C-5), 106.2 (d, C-1), 127.4, 127.7, 127.8, 127.8, 128.1,
128.3 (15d, arom. C-H), 138.0, 138.0, 138.8 (3 s, arom. C-CH2O);
Elemental analysis(%) calcd for: C29H34O5 C 75.30, H 7.41; found:
C 75.33, H 7.48; Mass (ESI-MS); m/z 485.28(M + Na)+.
lacto-4a. 1.75 g (83%) of a pale yellow syrup; Rf 0.41 (hex-
ane/ethyl acetate 2 : 1); [a]2D0 = +13.2 (c = 1.01 in CHCl3); IR
(film): v = 3035, 2941, 1836, 1752, 1647, 1497, 1480, 1335, 1210,
1151 cm-1; 1H NMR (500 MHz, CDCl3): d = 2.24 (dddd, J = 11.2,
8.5, 6.3, 5.4 Hz, 1H, 2-H), 2.80 (dd, J = 15.3, 6.3 Hz, 1H, 13-H),
2.87 (dd, J = 15.5, 5.4 Hz, 1H, 13¢-H), 3.1 (m, 4H, 5-H, 11-H),
3.42 (s, 3H, OMe), 3.44 (dd, J = 11.0, 8.8 Hz, 2H, 12-H), 3.65 (dd,
J = 9.5, 7.9, Hz, 2H, 6-H), 3.81 (dd, J = 11.2, 10.1 Hz, 1H, 3-H),
3.81 (dd, J = 9.0, 3.8 Hz, 1H, 9-H), 4.00 (t, J = 9.0, 9.0 Hz, 1H,
8-H), 4.18 (d, J = 11.5 Hz, 1H, CH2Ph), 4.27 (d, J = 12.2 Hz, 1H,
CH2Ph), 4.27 (d, J = 12.2 Hz, CH2Ph), 4.28 (d, J = 8.5 Hz, 1H,
1-H), 4.33 (d, J = 12.2 Hz, 1H, CH2Ph), 4.37 (d, J = 9.0 Hz, 1H,
7-H), 4.43 (d, J = 11.5 Hz, 1H, CH2Ph), 4.44 (d, J = 12.0 Hz, 1H,
CH2Ph), 4.53 (d, J = 12.0 Hz, 1H, CH2Ph), 4.62 (d, J = 10.1, 2.2
Hz, 1H, 4-H), 4.62 (dd, J = 3.8, 2.5 Hz 1H 10-H), 4.87 (d, J = 12.0
Hz, 1H, CH2Ph), 5.14 (d, J = 10.2 Hz, 1H, CH2Ph), 6.20 (dt, J =
7.0, 1.8 Hz 1H thiopyr. C-H), 6.87 (dd, J = 7.0, 1.8, Hz, 1H thiopyr.
C-H), 7.01 (dt, J = 7.0, 1.8 Hz 1H thiopyr. C-H), 7.01–7.29 (m,
30H, arom. H), 7.52 (dd, J = 7.0, 1.8 Hz, 1H thiopyr. C-H);13C
NMR (125 MHz, CDCl3): d = 30.6 (t, C-13), 44.4 (d, C-2), 56.8 (q,
OMe), 68.0, 68.1 (2t, C-6, C-12), 72.60, 73.0, 73.6, 74.3, 74.5, 75.2
xylo-5. 525 mg (77%) of a colorless syrup; Rf 0.42 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +28.4 (c = 1.02 in CHCl3); IR
(film): v = 2917, 2849, 1496, 1454, 1367, 1204, 1175, 1091, 1072,
1028 cm-1; 1H NMR (300 MHz, CDCl3): d = 0.97 (d, J = 6.6 Hz,
3H, CH3), 1.61 (ddq, J = 11.6, 8.4, 6.6 Hz, 1H, 2-H), 3.12 (ddd, J =
9.7, 8.5, 1.8 Hz, 2H, 5-H), 3.38 (s, 3H, OMe), 3.54 (ddd, J = 9.7,
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8.5, 5.1, Hz, 1H, 4-H), 3.89 (d, J = 8.4 Hz, 1H, 1-H), 3.94 (dd, J =
11.5, 5.1 Hz, 1H, 3-H), 4.55 (d, J = 11.5 Hz, 1H, CH2Ph), 4.57 (d,
J = 11.0 Hz, 1H, CH2-Ph), 4.62 (d, J = 11.5 Hz, 1H, CH2Ph), 4.85
(d, J = 11.0 Hz, 1H, CH2Ph), 7.20–7.27 (m, 10H, arom. H); 13C
NMR (75 MHz, CDCl3): d = 12.8 (q, CH3), 41.7 (d, C-2), 56.5 (q,
OMe), 63.6 (t, C-5), 72.6, 74.8, (2t, CH2Ph), 79.1, 83.4 (3d, C-3,
C-4), 106.0 (d, C-1), 127.5, 127.6, 127.8, 128.0, 128.3 (10d, arom.
C-H), 138.2, 138.5, (2 s, arom. C-CH2O); Elemental analysis(%)
calcd for: C21H26O4 C 73.66, H 7.65; found: C 73.61, H 7.80; Mass
(ESI-MS); m/z 365.56(M + Na)+
1151 cm-1; 1H NMR (300 MHz, CDCl3): d = 1.16 (d, J = 6.4, Hz,
3H, CH3), 1.84 (ddq, J = 10.6, 8.7, 6.4, Hz, 1H, 2-H), 3.23 (dd, J =
10.6, 8.7 Hz, 1H, 3-H), 3.56 (s, 3H, OMe), 3.63 (d, J = 9.8 Hz, 1H,
9-H), 3.41 (dd J = 6.5, 4.6 Hz, 1H, 6-H), 3.43 (dd, J = 7.2, 5.3 Hz,
1H, 12-H), 3.45 (dd, J = 6.5, 3.6 Hz, 1H, 6¢-H), 3.48 (dd, J = 7.2,
6.0 Hz, 1H, 12¢-H), 3.80 (ddd, J = 8.3, 4.6, 3.6 Hz, 1H, 5-H), 3.84
(ddd, J = 6.0, 5.3, 2.0 Hz, 1H, 11-H), 3.92 (dd, J = 9.8, 2.3 Hz,
1H, 8-H), 3.99 (d, J = 2.0 Hz, 1H, 10-H), 4.04 (dd, J = 8.7, 8.3 Hz,
1H, 4-H), 4.08 (d, J = 8.7, 3.6 Hz, 1H, 1-H), 4.29 (d, J = 11.7 Hz,
1H, CH2Ph), 4.40 (d, J = 11.7 Hz, 1H, CH2Ph), 4.48 (d, J = 11.4
Hz, 1H, CH2Ph), 4.48 (d, J = 10.2 Hz, 1H, CH2Ph), 4.57 (d, J =
10.0 Hz, 1H, CH2Ph), 4.61 (d, J = 10.0 Hz, 1H, CH2Ph), 4.66 (d,
J = 10.0 Hz, 1H, CH2Ph), 4.78 (d, J = 10.5 Hz, 1H, CH2Ph), 4.87
(dd, J = 11.0 Hz, 1H, CH2Ph), 4.89 (d, J = 2.3 Hz, 1H, 7-H), (d,
J = 11.0 Hz, 1H, CH2Ph), 5.05 (d, J = 11.2 Hz, 1H, CH2Ph), 5.18
(d, J = 10.5 Hz, 1H, CH2Ph), 7.17–7.41 (m, 30H, arom. H), 13C
NMR (75 MHz, CDCl3): d = 13.6 (q, CH3), 43.1 (d, C-2), 57.6 (q,
OMe), 69.0, 69.5 (2t, C-6, C-12), 73.6, 74.0, 74.3, 75.6, 75.7, 76.2
(6t, CH2Ph), 73.9, 74.8, 76.5, 78.2, 81.1, 83.4, 84.1 (7d, C-3, C-4,
C-5, C-8, C-9, C-10, C-11), 103.8, 106.7, (2d, C-1, C-7), 128.1,
128.2, 128.3, 128.4, 128.4, 128.5, 128.6, 128.7, 128.9, 129.0, 129.1,
129.3, (30d, arom. C-H), 139.1, 139.5, 139.6, 139.8, 140.0, 140.1,
(6 s, arom. C-CH2O); Elemental analysis(%) calcd for: C56H62O10
C 75.14, H 6.98; found: C 75.28, H 7.99; Mass (ESI-MS); m/z
894.54(M)+.
arabino-5. 490 mg (71%) of a colorless syrup; Rf 0.40 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +13.9 (c = 1.02 in CHCl3); IR
(film): v = 2912, 2846, 1494, 1451, 1362, 1204, 1178, 1093, 1072,
1021 cm-1; 1H NMR (300 MHz, CDCl3): d = 0.95 (d, J = 6.6 Hz,
3H, CH3), 2.11 (ddq, J = 10.6, 8.2, 6.6 Hz, 1H, 2-H), 3.0 (dd, J =
10.6, 3.0 1H, 3-H), 3.18 (d, J = 12.8 1H, 5-H), 3.38 (s, 3H, OMe),
3.53 (dd, J = 3.0, 2.6 Hz, 1H, 4-H), 3.81 (d, J = 8.2 Hz, 1H. 1-H),
4.06 (dd, J = 12.8, 2.6 Hz, 1H, 5¢-H), 4.24 (d, J = 11.9 Hz, 1H,
CH2Ph), 4.46 (d, J = 11.9 Hz, 1H, CH2-Ph), 4.52 (d, J = 12.6 Hz,
1H, CH2Ph), 4.68 (d, J = 12.6 Hz, 1H, CH2Ph), 7.13–7.30 (m, 10H,
arom. H); 13C NMR (75 MHz, CDCl3): d = 12.5 (q, CH3), 37.4 (d,
C-2), 56.4 (q, OMe), 63.0 (t, C-5), 70.7, 70.7, (2t, CH2Ph), 69.6,
80.6 (3d, C-3, C-4), 106.1 (d, C-1), 127.4, 127.5, 127.6, 127.8, 128.2
(10d, arom. C-H), 138.0, 138.3 (2 s, arom. C-CH2O); Elemental
analysis(%) calcd for: C21H26O4 C 73.66, H 7.65; found: C 73.56,
H 7.78; Mass (ESI-MS); m/z 365.54(M + Na)+.
General procedure for the bromination of Barton esters 4a
malto-5. 1.20 g (68%) of a colorless syrup; Rf 0.56 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +36.9 (c = 1.02 in CHCl3); IR
(film): v = 3032, 2943, 1833, 1753, 1649, 1495, 1483, 1339, 1211,
1153 cm-1; 1H NMR (500 MHz, CDCl3): d = 1.00 (d, J = 4.1, Hz,
3H, CH3), 1.68 (ddq, J = 9.8, 8.6, 4.1, Hz, 1H, 2-H), 3.07 (dd, J =
9.8, 8.5 Hz 1H, 3-H), 3.27 (dd, J = 6.8, 4.2 Hz, 1H, 6-H), 3.28 (dd,
J = 6.8, 3.8 Hz, 1H, 6¢-H), 3.29 (dd, J = 7.6, 5.2 Hz, 1H, 12-H),
3.30 (dd, J = 7.6, 3.0 Hz, 1H, 12¢-H), 3.40 (s, 3H, OMe), 3.44 (dd,
J = 9.8, 8.6 Hz, 1H, 9-H), 3.67 (ddd J = 8.4, 4.2, 3.8 Hz, 1H, 5-H),
3.69 (ddd, J = 7.8, 5.2, 3.6 Hz 1H, 11-H), 3.74 (dd, J = 8.4, 8.3 Hz,
1H, 4-H), 3.83 (dd J = 9.8, 7.8 Hz, 1H, 10-H), 3.89 (d, J = 2.4 Hz,
1H, 7-H), 3.92 (dd J = 8.6, 2.4 Hz, 1H, 8-H), 4.15 (d, J = 12.0 Hz,
1H, CH2Ph), 4.26 (d, J = 12.8 Hz, 1H CH2Ph), 4.33(d, J = 12.0
Hz, 1H, CH2Ph), 4.36 (d, J = 8.6 Hz, 1H, 1-H), 4.41 (d, J = 10.0
Hz, 1H, CH2Ph), 4.46 (d, J = 11.0 Hz, 1H, CH2Ph), 4.47 (d, J =
12.0 Hz, 1H, CH2Ph), 4.50 (d, J = 12.0 Hz, 1H, CH2Ph), 4.65 (d,
J = 10.0 Hz, 1H, CH2Ph), 4.72 (d, J = 11.0 Hz 1H CH2Ph), 4.76
(d, J = 11.0 Hz, 1H, CH2Ph) 4.89 (d, J = 112.0 Hz, 1H, CH2Ph),
5.03,(d, J = 11.0 Hz, 1H, CH2Ph), 7.03–7.25 (m, 30H, arom. H),
13C NMR (125 MHz, CDCl3): d = 12.6 (q, CH3), 42.1 (d, C-2),
56.5 (q, OMe), 68.2, 68.6 (2t, C-6, C-12), 72.7, 73.1, 73.4, 74.6,
74.7, 75.2, (6t, CH2Ph), 73.0, 74.0, 75.6, 77.3, 80.2, 82.6, 83.2 (7d,
C-3, C-4, C-5, C-8, C-9, C-10, C-11), 103.8, 106.7 (2d, C-1, C-7),
127.0, 127.2, 127.3, 127.4, 127.5, 127.6, 127.8, 127.9, 128.0, 128.1,
128.3(30d, arom. C-H), 138.2, 138.6, 138.6, 138.9, 139.1, 139.1
(6 s, arom. C-CH2O); Elemental analysis(%) calcd for: C56H62O10
C 75.14, H 6.98; found: C 75.27, H 7.18; Mass (ESI-MS); m/z
894.54(M)+.
The Barton ester 4a (2.0 mmol) was dissolved in 20 mL of dry
benzene and was protected from light with aluminium foil under
argon atmosphere. Bromotrichloromethane (795 mg, 4.0 mmol)
was added at 25 ◦C. The reaction mixture was subsequently
exposed to light using a 250 W low- pressure mercury lamp.
After completion of the reaction (approximately 1–2 h), the crude
reaction mixture was concentrated and the residue was purified by
flash chromatography, affording the products 6.
gluco-6. 825 mg (76%) of a colorless syrup; Rf 0.54 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +14.6 (c = 1.02 in CHCl3); IR
(film): v = 3063, 3029, 2858, 1950, 1732, 1496, 1362, 1421,1312,
1
1100, 1027 cm-1; H NMR (300 MHz, CDCl3): d = 1.75 (dddd,
J = 10.4, 8.1, 2.8, 2.4 Hz, 1H, 2-H), 3.38 (ddd, J = 9.5, 3.5, 3.0 Hz,
1H, 5-H), 3.46 (s, 3H, OMe), 3.60 (dd, J = 9.5, 8.8 Hz, 1H, 4-H),
3.67 (dd, J = 11.9, 2.8 Hz, 1H, 7-H), 3.68 (dd, J = 11.9, 2.0 Hz,
1H, 7¢-H), 3.70 (dd, J = 10.5, 3.5 Hz, 1H, 6-H), 3.71 (dd, J = 10.5,
3.0 Hz, 1H, 6¢-H), 3.76 (dd, J = 10.4, 8.8 Hz, 1H, 3-H), 4.32 (d,
J = 8.1 Hz, 1H, 1-H), 4.46 (d, J = 12.0 Hz, 1H, CH2Ph), 4.50 (d,
J = 10.7 Hz, 1H, CH2Ph), 4.56 (d, J = 12.0 Hz, 1H, CH2Ph), 4.69
(d, J = 10.8 Hz, 1H, CH2Ph), 4.71 (d, J = 10.8 Hz, 1H, CH2Ph),
4.86 (d, J = 10.7 Hz, 1H, CH2Ph), 7.08–7.28 (m, 15H, arom. H);
13C NMR (75 MHz, CDCl3): d = 31.5 (t, C-7), 47.5 (d, C-2), 57.1
(q, OMe), 68.8 (d, C-6), 73.4, 74.7, 75.4 (3t, CH2Ph), 74.9, 79.7,
79.8 (3d, C-3, C-4, C-5), 102.15 (d, C-1), 127.5, 127.7, 127.7, 128.3,
128.4, 128.4 (15d, arom. C-H), 137.9, 138.1, 138.2 (3 s, arom. C-
CH2O); elemental analysis(%) calcd for C29H33BrO5: C 64.33, H
6.14; found: C 64.39, H 6.19; Mass (ESI-MS); m/z 563.23(M +
Na)+.
lacto-5. 1.15 g (64%) of a colorless syrup; Rf 0.56 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +21.3 (c = 1.02 in CHCl3); IR
(film): v = 3035, 2941, 1836, 1752, 1647, 1497, 1480, 1335, 1210,
galacto-6. 800 mg (74%) of a colorless syrup; Rf 0.53 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +17.1 (c = 1.01 in CHCl3); IR
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(film): v = 3030, 2918, 1496, 1363, 1250,1100, 1086 cm-1; 1H NMR
(300 MHz, CDCl3): d = 2.20 (dddd, J = 10.8, 8.1, 2.6, 2.5 Hz, 1H,
2-H), 3.44 (s, 3H, OMe), 4.49 (ddd, J = 3.1, 2.3, 2.5 1H 5-H), 3.55
(dd, J = 12.3, 2.6 Hz, 2H, 7-H), 3.57 (dd, J = 12.3, 2.4 Hz, 2H,
7¢-H), 3.63 (d, J = 10.8 1H, 3-H), 3.73 (dd, J = 10.0, 3.1 Hz, 1H,
6-H), 3.82 (dd, J = 10.0, 2.3 Hz, 1H, 6¢-H), 3.88 (d, J = 2.5 Hz,
1H 4-H), 4.32 (d, J = 8.1 Hz, 1H, 1-H), 4.36 (d, J = 11.8 Hz, 1H,
CH2Ph), 4.42 (d, J = 11.8 Hz, 1H, CH2Ph), 4.47 (d, J = 11.0 Hz,
1H, CH2Ph), 4.51 (d, J = 11.7 Hz, 1H, CH2Ph), 4.65 (d, J = 11.0
Hz, 1H, CH2Ph), 4.78 (d, J = 11.7 Hz, 1H, CH2Ph), 7.16–7.29 (m,
15H, arom. H);13C NMR (75 MHz, CDCl3): d = 32.6 (dt C-7), 42.3
(d, C-2), 57.0 (q, OMe), 68.9 (d, C-6), 72.2, 73.5, 74.3 (3t, CH2Ph),
70.9, 73.4, 78.4 (C-3, C-4, C-5), 102.4 (C-1), 127.5, 127.7, 127.9,
128.0, 128.1, 128.4 (15d, arom. C-H), 37.7, 137.9, 138.6 (3 s, arom.
C-CH2O); Elemental analysis(%) calcd for C29H33BrO5: C 64.33,
H 6.14; found: C 64.36, H 6.21; Mass (ESI-MS); m/z 563.26(M +
Na)+.
6¢-H), 3.33(dd, J = 7.2, 5.6 Hz, 1H, 12¢-H), 3.44 (s, 3H, OMe),
3.46 (dd, J = 10.2, 6.5 Hz 1H, 3-H), 3.62(ddd J = 9.6, 4.5, 3.6 Hz,
1H, 5-H), 3.65(ddd, J = 8.9, 5.6, 5.0 Hz 1H, 11-H), 3.61 (dd, J =
2.1, 1.8 Hz, 1H, 10-H), 3.70(dd J = 9.8, 1.9 Hz, 1H, 9-H), 3.79
(dd, J = 10.8, 3.6 Hz, 1H, 13-H), 3.81 (dd, J = 10.8, 5.1 Hz, 1H,
13¢-H), 3.95 (dd, J = 9.8, 9.2 Hz, 1H, 8-H), 4.16(d, J = 11.8 Hz,
1H CH2Ph), 4.26(d, J = 12.6 Hz, 1H, CH2Ph) 4.28 (d, J = 10.5
Hz, 1H, CH2Ph), 4.30 (d, J = 12.0 Hz, 1H, CH2Ph), 4.49 (dd, J =
10.2, 9.6 Hz, 1H, 4-H), 4.50(d, J = 9.2 Hz, 1H, 7-H), 4.60 (d, J =
12.6 Hz, 1H, CH2Ph), 4.65(d, J = 12.0 Hz, 1H CH2Ph), 4.69(d,
J = 11.0 Hz, 1H, CH2Ph), 4.73(d, J = 11.5 Hz, 1H, CH2Ph), 4.77
(d, J = 11.8 Hz, 1H, CH2Ph), 4.90 (d, J = 11.5 Hz 1H CH2Ph),
5.15(d, J = 10.0 Hz, 1H, CH2Ph), 6.99–7.25 (m, 30H, arom. H),
13C NMR (125 MHz, CDCl3): d = 31.8 (t, C-13), 47.2 (d, C-2),
56.9 (q, OMe), 68.1, 68.2 (2t, C-6, C-12), 72.6, 73.0, 73.0, 73.3,
74.6, 75.3 (6t, CH2Ph), 73.0, 73.1 73.8, 77.3, 77.9, 80.1, 82.5 (7d,
C-3, C-4, C-5, C-8, C-9, C-10, C-11), 127.2, 127.3, 127.4, 127.5,
127.6, 127.8, 127.9, 128.1, 128.2, 128.3 (30d, arom. C-H), 138.1,
138.4, 138.5, 138.8, 138.9, 139.0 (6 s, arom. C-CH2O); Elemental
analysis(%) calcd for: C56H61BrO10 C 69.06 H 6.31; found: C 69.34
H 6.38; Mass (ESI-MS); m/z 973.58(M)+.
xylo-6. 600 mg (71%) of a colorless syrup; Rf 0.50 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +9.6 (c = 1.01 in CHCl3); IR (film):
v = 2915, 2842, 1455, 1454, 1368, 1202, 1178, 1091, 1077, 1022
cm-1; 1H NMR (300 MHz, CDCl3): d = 1.68 (dddd, J = 9.8, 8.0,
3.0, 2.5 Hz, 1H, 2-H), 3.15 (dd, J = 11.6, 9.8 1H, 5-H), 3.42 (s,
3H, OMe), 3.58 (ddd, J = 10.2, 9.8, 5.0 Hz, 1H, 4-H), 3.62 (dd,
1H, J = 10.2, 9.8 Hz, 3-H), 3.65 (dd, J = 10.0, 3.0 Hz, 1H, 6-H),
3.71 (dd, J = 10.0, 2.5 Hz, 1H, 6¢-H), 3.92 (dd, J = 11.6, 5.0 Hz,
1H, 5¢-H), 4.28 (d, J = 8.0 Hz, 1H, 1-H), 4.54 (d, J = 11.5 Hz, 1H,
CH2Ph), 4.60 (d, J = 11.5 Hz, 1H, CH2-Ph), 4.66 (d, J = 10.8 Hz,
1H, CH2Ph), 4.91 (d, J = 10.8 Hz, 1H, CH2Ph), 7.17–7.26 (m, 10H,
arom. H); 13C NMR (75 MHz, CDCl3): 31.7 (t, C-7), 46.9 (d, C-2),
57.0 (q, OMe), 63.5 (t, C-5), 72.8, 75.3 (2t, CH2Ph), 78.5, 79.5 (3d,
C-3, C-4), 102.6 (d, C-1), 127.7, 127.8, 127.9, 128.0, 128.4, 128.4
(10d, arom. C-H), 138.0, 138.4, (2 s, arom. C-CH2O); Elemental
analysis(%) calcd for: C21H25BrO4 C 59.86, H 5.98; found: C 59.95,
H 6.09; Mass (ESI-MS); m/z 420.16(M)+.
lacto-6. 1.35 g (69%) of a colorless syrup; Rf 0.60 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +36.3 (c = 1.01 in CHCl3); IR
(film): v = 3035, 2941, 1836, 1752, 1647, 1497, 1480, 1335, 1210,
1151 cm-1; 1H NMR (300 MHz, CDCl3): d = 1.73 (dddd, J = 8.6,
6.5, 5.1, 3.6, Hz 1H, 2-H), 3.27 (dd J = 6.3, 4.5 Hz, 1H, 6-H), 3.29
(dd, J = 7.2, 5.0 Hz, 1H, 12-H), 3.30 (dd, J = 6.3, 3.6 Hz, 1H,
6¢-H), 3.33(dd, J = 7.2, 5.6 Hz, 1H, 12¢-H), 3.44 (s, 3H, OMe),
3.46 (dd, J = 10.2, 6.5 Hz 1H, 3-H), 3.62 (ddd J = 9.6, 4.5, 3.6 Hz,
1H, 5-H), 3.65 (ddd, J = 8.9, 5.6, 5.0 Hz 1H, 11-H), 3.61 (dd, J =
2.1, 1.8 Hz, 1H, 10-H), 3.70 (dd J = 9.8, 1.9 Hz, 1H, 9-H), 3.79
(dd, J = 10.8, 3.6 Hz, 1H, 13-H), 3.81 (dd, J = 10.8, 5.1 Hz, 1H,
13¢-H), 3.95 (dd, J = 9.8, 9.2 Hz, 1H, 8-H), 4.16 (d, J = 11.8 Hz,
1H CH2Ph), 4.26 (d, J = 12.6 Hz, 1H, CH2Ph), 4.28 (d, J = 10.5
Hz, 1H, CH2Ph), 4.30 (d, J = 12.0 Hz, 1H, CH2Ph), 4.49 (dd, J =
10.2, 9.6 Hz, 1H, 4-H), 4.50 (d, J = 9.2 Hz, 1H, 7-H), 4.60 (d, J =
12.6 Hz, 1H, CH2Ph), 4.65 (d, J = 12.0 Hz, 1H CH2Ph), 4.69 (d,
J = 11.0 Hz, 1H, CH2Ph), 4.73 (d, J = 11.5 Hz, 1H, CH2Ph), 4.77
(d, J = 11.8 Hz, 1H, CH2Ph), 4.90 (d, J = 11.5 Hz 1H CH2Ph),
5.15(d, J = 10.0 Hz, 1H, CH2Ph), 6.99–7.25 (m, 30H, arom. H),
13C NMR (125 MHz, CDCl3): d = 31.9 (t, C-13), 47.2 (d, C-2),
57.1 (q, OMe), 68.0, 68.2 (2t, C-6, C-12), 72.6, 73.1, 73.4, 74.7,
75.2, 75.4 (6t, CH2Ph), 73.0, 73.7, 75.2, 77.33 78.0, 80.0, 82.4 (7d,
C-3, C-4, C-5, C-8, C-9, C-10, C-11), 127.3, 127.4, 127.5, 127.5,
127.6, 127.9, 128.0, 128.2, 128.31, 128.3, (30d, arom. C-H), 138.1,
138.4, 138.5, 138.7, 138.8, 139.0 (6 s, arom. C-CH2O); Elemental
analysis(%) calcd for: C56H61BrO10 C 69.06 H 6.31; found: C 69.44
H 6.42; Mass (ESI-MS); m/z 973.56(M)+.
arabino-6. 615 mg (73%) of a white solid; m.p. 109 ◦C; Rf 0.48
(hexane/ethyl acetate 6 : 1); [a]2D0 = +25.2 (c = 1.02 in CHCl3); IR
(film): v = 2920, 2832, 1448, 1444, 1362, 1211, 1188, 1084, 1076,
1028 cm-1; 1H NMR (300 MHz, CDCl3): d = 1.68 (dddd, J = 12.8,
7.7, 2.3, 2.0 Hz, 1H, 2-H), 3.21 (d, J = 12.8 1H, 3-H), 3.45 (s, 3H,
OMe), 3.56 (dd, J = 10.5, 1.8 Hz, 1H, 5-H), 3.58 (dd, J = 10.5,
2.0 Hz, 1H, 5¢-H), 3.73 (dd, J = 10.0, 2.0 Hz, 1H, 6-H), 3.82 (dd,
J = 10.0, 2.3 Hz, 1H, 6¢-H), 4.06 (dd, J = 1.8, 2.0 Hz, 1H, 4-H),
4.23 (d, J = 7.8 Hz, 1H, 1-H), 4.36 (d, J = 11.0 Hz, 1H, CH2Ph),
4.48 (d, J = 11.0 Hz, 1H, CH2Ph), 4.54 (d, J = 12.30 Hz, 1H,
CH2Ph), 4.69 (d, J = 12.30 Hz, 1H, CH2Ph), 7.19–7.31 (m, 10H,
arom. H); 13C NMR (75 MHz, CDCl3): 32.5 (t, C-7), 42.5 (d, C-2),
56.9 (q, OMe), 63.3 (t, C-5), 71.1, 71.5 (2t, CH2Ph), 70.1, 76.5 (3d,
C-3, C-4), 102.9 (d, C-1), 127.6, 127.8, 127.9, 128.0, 128.3, 128.4,
(10d, arom. C-H), 137.8, 138.3 (2 s, arom. C-CH2O); Elemental
analysis(%) calcd for: C21H25BrO4 C 59.86, H 5.98; found: C 59.88
H 6.01; Mass (ESI-MS); m/z 420.13(M)+.
Acknowledgements
We thank the University of Potsdam for generous financial
support.
malto-6. 1.37 g (70%) of a colorless syrup; Rf 0.60 (hex-
ane/ethyl acetate 6 : 1); [a]2D0 = +13.8 (c = 1.02 in CHCl3); IR
(film): v = 3045, 2948, 1837, 1751, 1648, 1497, 1481, 1331, 1210,
1152 cm-1; 1H NMR (300 MHz, CDCl3): d = 1.73(dddd, J = 8.6,
6.5, 5.1, 3.6, Hz 1H, 2-H), 3.27(dd J = 6.3, 4.5 Hz, 1H, 6-H), 3.29
(dd, J = 7.2, 5.0 Hz, 1H, 12-H), 3.30 (dd, J = 6.3, 3.6 Hz, 1H,
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