New derivatives of D-mannaric and galactaric acids. Synthesis of a new stereoregular Nylon 66 analog from carbohydrate-based monomers having the D-manno configuration

Article abstract of DOI:10.1016/S0008-6215(03)00093-4

2,3,4,5-Tetra-O-methyl-D-mannaric and galactaric acids and their bis(pentachlorophenyl) esters have been prepared as crystalline compounds, in good yields, from D-mannitol and galactitol, respectively. A new stereoregular polyamide, analogous to Nylon 66,

Full text of DOI:10.1016/S0008-6215(03)00093-4

Carbohydrate Research 338 (2003) 1115–1119
www.elsevier.com/locate/carres
Note
New derivatives of
Synthesis of a new stereoregular Nylon 66 analog from
carbohydrate-based monomers having the -manno configuration
D-mannaric and galactaric acids.
D
Manuel Mancera, Isaac Roffe´, Manuel Rivas, Juan A. Galbis*
Departamento de Qu´ımica Orga´nica y Farmace´utica, Uni6ersidad de Se6illa, E-41071 Se6illa, Spain
Received 8 January 2003; received in revised form 18 February 2003; accepted 22 February 2003
Abstract
2,3,4,5-Tetra-O-methyl-
crystalline compounds, in good yields, from
Nylon 66, has been prepared by polycondensation of bis(pentachlorophenyl) 2,3,4,5-tetra-O-methyl-
amino-1,6-dideoxy-2,3,4,5-tetra-O-methyl- -mannitol dihydrochloride. The polymer has a Mw of 31,100 with a polydispersity of
D
-mannaric and galactaric acids and their bis(pentachlorophenyl) esters have been prepared as
-mannitol and galactitol, respectively. A new stereoregular polyamide, analogous to
-mannarate with 1,6-di-
D
D
D
1.5 (GPC). It was highly hygroscopic and soluble in ethanol, acetone, dimethyl sulfoxide, N,N-dimethylformamide and
chloroform, but only slightly soluble in water. © 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Stereoregular polyamides; Regioregular polyamides;
D
-Mannaric acid, protected; Galactaric acid, protected; Carbohydrate-based
monomers; Polycondensation
1. Introduction
ties of a stereo- and regioregular polyamide, analogous
to Nylon 66, by polycondensation of 11 with 1,6-di-
In the last few years, efforts have been devoted to
preparing linear polyamides, analogous to the industrial
Nylons, but more hydrophilic and degradable, in order
to extend their applications to new fields demanding
materials either with lower environmental impact or
displaying biodegradable and biocompatible proper-
ties.1 The use of monomers derived from carbohydrates
in the design of polyamides with enhanced hydrophilic-
ity and biodegradability constitutes an interesting strat-
egy that is being intensively explored.2–4 We have
recently reported carbohydrate-based monomers which
have been used for the preparation of new regio- and
amino-1,6-dideoxy-2,3,4,5-tetra-O-methyl-
D-mannitol
dihydrochloride (13).5
2. Results and discussion
The synthesis of esters 11 and 12 was carried out by
protection of the primary hydroxyl groups of -manni-
D
tol (1) and galactitol (2) as their triphenylmethyl deriva-
tives (3)7 and (4)8 (Scheme 1). O-Methylation of the
secondary hydroxyl groups of 3 and 4 with methyl
iodide and potassium hydroxide in dimethyl sulfoxide
gave 5 and 6, respectively. These compounds could be
easily detritylated by hydrogenation in the presence of
palladium to give the corresponding tetra-O-methyl
alcohols 7 and 8. After oxidation of the terminal car-
bons with nitric acid at 70–80 °C, the tetra-O-methyl-
stereoregular AABB-type polyamides derived from
mannitol and
-iditol.5,6 In this paper we describe the
preparation of 2,3,4,5-tetra-O-methyl- -mannaric acid
D-
L
D
(9) and 2,3,4,5-tetra-O-methylgalactaric acid (10), as
well as their bis(pentachlorophenyl) esters 11 and 12,
respectively. We also describe the synthesis and proper-
D-mannaric (9) and tetra-O-methylgalactaric acids (10)
were obtained. The active bis(pentachlorophenyl) esters
11 and 12 were obtained in good yield as crystalline
compounds from the corresponding aldaric acids with
* Corresponding author. Tel.: +34-95-4556736; fax: +34-
95-4556737
E-mail address: jgalbis@us.es (J.A. Galbis).
0008-6215/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0008-6215(03)00093-4

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M. Mancera et al. / Carbohydrate Research 338 (2003) 1115–1119
such behavior is unusual in conventional polyamides, it
is quite common in stereoregular polyamides containing
stereocenters in the main chain.10 This is currently
interpreted as being a consequence of the occurrence of
ordered helical conformations stabilized by intramolec-
ular hydrogen bonds.11 On the other hand, this
polyamide is only slightly soluble in water, although it
displays elevated hydrophilicity due to the presence in
the chain of the hydrophilic methoxyl groups.
pentachlorophenol and dicyclohexylcarbodiimide in
dichloromethane. Their structure was confirmed by IR
and NMR spectroscopies, mass spectrometry and mi-
1
croanalytical data. The H and 13C NMR data were in
agreement with the expected symmetry in both
diastereomers.
Polycondensation of the active ester 11 with the
diamine 13 was conducted in N-methylpyrrolidinone
(NMP) as solvent at 45 °C for 7 days (Scheme 2). The
polyamide 14 was obtained as a solid compound which
was purified by repeatedly pouring a dichloromethane
solution of the polymer into diethyl ether and filtration
of the precipitate. The presence of eight methoxyl
groups in the repeating unit makes this polyamide
markedly hygroscopic, an effect that increases with the
number of such groups in the polymer chains.9 Com-
plete removal of the moisture was not possible even
under severe conditions of drying, as seen by microana-
lytical data. The presence of the amide functional group
was confirmed by the characteristic IR absorptions for
the NꢀH stretching and the amide I and II bands (3433,
1669, and 1537 cm−1, respectively).
The molecular-weight distribution of the polyamide
was studied by gel permeation chromatography (GPC)
using Styragel columns with chloroform as the mobile
phase. The Mw value is 31,100 with a polydispersity
ratio (Mw/Mn) of 1.5. The thermal behavior of the
polyamide was examined by differential scanning
calorimetry (DSC). During the first heating cycle (−10
to 230 °C), it showed a very sharp endotherm of melt-
ing (TmI=204 °C, DHmI=65.9 j g−1) preceded by a
broader exotherm peak (193 °C) due to crystallization.
From 235 °C, decomposition started. A second heating
cycle of a rapidly quenched sample after melting
showed the glass-transition (Tg=67 °C) and a broad
endotherm of melting (TmII=228 °C, DHmII 16.9 j
The synthesized polyamide was optically active, and
was soluble in ethanol, acetone, dimethyl sulfoxide,
N,N-dimethylformamide, and chloroform. The solubil-
ity in chloroform is worth mentioning, because while
g
−1).
Since the two monomers possess a C2 symmetry axis,
the
D-manno-polyamide 14 was regio- and stereoregu-
Scheme 1. (a) Ph3CCl, pyridine; (b) MeI, KOH, DMSO; (c) H2, Pd–C, MeOH; (d) 60% HNO3; (e) PcpOH, DCC, NMP. Pcp:
pentachlorophenyl; DCC: dicyclohexylcarbodiimide; NMP: N-methylpyrrolidinone.
Scheme 2. Pcp: pentachlorophenyl; DCC: dicyclohexylcarbodiimide; NMP: N-methylpyrrolidinone.

M. Mancera et al. / Carbohydrate Research 338 (2003) 1115–1119
1117
lar, as was confirmed by its NMR spectra. The absence
of 1,3-dipolar interactions between the methoxyl groups
allows an extended planar zigzag conformation as the
preponderant of both monomers in solution.12,13 How-
ever, the preponderant conformation of the polyamide
in chloroform solution must be different, as revealed by
the value of Jꢀ0 Hz (7.2 Hz in the monomer 11)
between H-3/4 and H-2/5, which appear as singlets,
indicating a rotation around the C2(5)ꢀC3(4) bonds, re-
sulting preferentially in a ‘bent’ or ‘sickle’ conforma-
tion. This rotation may be a consequence of the regular
helical conformation stabilized by intramolecular hy-
drogen bonds that, as was pointed out above, such
polyamides can adopt in chloroform solution.11
poured into ice and water (2.5 L). The precipitated
mass was removed by filtration and dried on P2O5 to
give 3 as a solid (62.9 g, 91%): m.p. 90–93 °C (lit.7:
97–103 °C); [h]D −10° (c 1, CHCl3); IR: w 3409 (OH),
1
3088, 3030 (Ph) cm−1. H NMR (CDCl3, 200 MHz): l
2.47 (s, 4 H, 4 OH), 3.23 (dd, 2 H, J1,2 (5,6) 4.9, J1,1% (6,6%)
9.6 Hz, H-1/6), 3.28 (dd, 2 H, J1%,2 (5,6%) 5.7 Hz, H-1%/6%),
3.77 (d, 2 H, J2,3 (4,5) 6.3 Hz, H-3/4), 3.92 (m, 2 H,
H-2/5), 7.15-7.42 (m, 30 H, Ph); 13C NMR (50 MHz): l
64.9 (C-1/6), 70.3 (C-3/4), 71.7 (C-2/5), 86.7 (CꢀPh),
126.9, 127.7, 128,4, 143.5 (Ph). HRMS (FAB): [M+
Na]+ found 689.2860; requires 689.2879. Anal. Calcd
for C44H42O6: C, 79.28; H, 6.31. Found: C, 79.10; H,
6.10.
3.3. 1,6-Di-O-trityl-galactitol (4)
3. Experimental
To a solution of 2 (10 g, 54.9 mmol) in dry pyridine
(200 mL) was added trityl chloride (30.6 mg, 109.8
mmol). The mixture was stirred at room temperature
(rt) for 7 days, crystallized on standing for 1 day. The
precipitated mass was removed by filtration and washed
with pyridine and water, yield 32.4 g (89%): m.p.
183–184 °C (lit.8: 183–184 °C); IR: w 3303 (OH), 3088,
3.1. General methods
Chemicals were all used as purchased from Aldrich
Chemical Co. Solvents were dried and purified, when
necessary, by appropriate standard procedures. Melting
points are uncorrected. Thin layer chromatography
(TLC) was performed on Silica Gel 60 F254 (E. Merck)
with detection by UV light or charring with H2SO4.
Flash-column chromatography was performed using
Silica Gel 60 (230–400 mesh, E. Merck). Elemental
analyses were determined in the Microanalysis Labora-
tories of the CSIC, Isla de la Cartuja, Sevilla. IR
spectra (films or KBr discs) were recorded with a
JASCO FT/IR-410 spectrometer. NMR spectra were
recorded on a Bruker 200 AC-P. Optical rotations were
measured at 2095 °C with a Bellingham and Standley
Inc., P20 polarimeter. FABMS analyses were per-
formed on a double-focusing Kratos MS 80RFA mass
spectrometer equipped with the standard FAB source.
Argon was used as the bombarding gas. Spectra were
obtained using nitrobenzene–NaI as a matrix. Differen-
tial scanning calorimetry (DSC) was studied on a
calorimeter Perkin–Elmer DSC series 7, calibrated with
indium. Samples of about 2–3 mg were heated under
N2 at a rate of 20 °C min−1. Gel permeation chro-
matography (GPC) was performed in a Waters appara-
tus equipped with a Waters 2414 refractive index
detector and two styragel® HR columns (7.8×300 mm)
linked in series, thermostated at 35 °C, using chloro-
1
3030 (Ph) cm−1. H NMR (CDCl3, 200 MHz): l 2.43
(bs, 4 H, 4 OH), 3.24 (dd, 1 H, J1,2 (5,6) 5.8, J1,1% (6,6%) 9.6
Hz, H-1/6), 3.38 (dd, 1 H, J1%,2 4.3 Hz, H-1%/6%), 3.57 (s,
2 H, J2,3 (4,5) 0.0 Hz, H-3/4), 4.00 (t, 2 H, H-2/5,),
7.21–8.62 (m 30 H, Ph); 13C NMR (50 MHz): l 65.8
(C-1/6), 68.4 (C-3/4), 69.9 (C-2/5), 85.7 (CꢀPh), 126.8,
127.5, 127.8, 144.2 (Ph). HRMS (FAB): [M+Na]+
found 689.2892; requires 689.2879. Anal. Calcd for
C44H42O6: C, 79.28; H, 6.31. Found: C, 79.08; H, 6.15.
3.4. 2,3,4,5-Tetra-O-methyl-1,6-di-O-trityl-D-mannitol
(5)
To a solution of 3 (30 g, 45 mmol) in dry Me2SO (450
mL) were added KOH (60.6 g, 1.080 mol) and MeI
(33.6 mL, 540 mmol). The mixture was stirred at rt for
14 h and the resulting suspension was cooled and
treated with CH2Cl2 (500 mL). The salts were filtered
off, and the filtrate was washed with water (9×200
mL). The organic layer was dried (anhyd Na2SO4) and
concentrated to give an oily residue, which crystallized
after treatment with MeOH (20.0 g, 61%): mp 158–
160 °C; [h]D +2.0° (c 1, CHCl3); IR: w 3051, 2929 (Ph),
1
form as the mobile phase at a flow rate of 1 mL min−1
.
1592, 1486, 1443, 1101, 765, 704, 634 cm−1. H NMR
Molecular weight were estimated against polystyrene
standards.
(CDCl3, 200 MHz): l 3.07 (dd, 2 H, J1,2 (5,6) 4.2, J1,1%
(6,6%) 10.2 Hz, H-1/6), 3.17 (s, 6 H, OMe-3/4), 3.40 (m,
2 H, J2,3 (4,5) 8.3, J1%,2 (5,6%) 2.0 Hz, H-2/5) 3.47 (s, 6 H,
OMe-2/5), 3.52 (dd, 2 H, H-1%/6%), 3.71 (d, 2 H, H-3/4),
7.21–7.54 (m, 30 H, Ph); 13C NMR (50 MHz): l 57.7
(OMe-2/5), 60.4 (OMe-3/4), 61.8 (C-1/6), 79.0 (C-3/4),
79.9 (C-2/5), 86.7 (CꢀPh), 126.8, 127.6, 128.7, 144.0
(Ph). HRMS (FAB): [M+Na]+ found 745.3508; re-
3.2. 1,6-Di-O-trityl-D-mannitol (3)
To a solution of 1 (18.2 g, 0.1 mol) in dry pyridine (150
mL) was added trityl chloride (55.7 mg, 0.2 mol). The
mixture was shaken intermittently for 10 days, and

1118
M. Mancera et al. / Carbohydrate Research 338 (2003) 1115–1119
quires 745.3505. Anal. Calcd for C48H50O6: C, 79.75; H,
6.97. Found: C, 79.80; H, 6.99.
Anal. Calcd for C10H22O6: C, 50.41; H, 9.31. Found: C,
50.19; H, 9.20.
3.5. 2,3,4,5-Tetra-O-methyl-1,6-di-O-trityl-galactitol (6)
3.8. 2,3,4,5-Tetra-O-methyl-D-mannaric acid (9)
To a solution of 4 (10 g, 15 mmol) in dry Me2SO (150
mL) was added KOH (20.2 g, 360 mmol) and IMe (11.2
mL, 180 mmol). The reaction mixture was stirred at rt
for 36 h, poured into an ice–water mixture and ex-
tracted with dichloromethane. The organic phase was
concentrated under reduced pressure to a residue that
was washed with MeOH to give 6 as a solid (8 g, 75%):
To a solution of 7 (8.8 g, 37 mmol) in water (7 mL) was
added HNO3 (60%, 14 mL) and the mixture was heated
at 70–80 °C with stirring for 24 h. The reaction was
diluted with water (280 mL) and the residue co-evapo-
rated several times with water and finally with toluene.
Flash-column chromatography (20:1 Cl2H2–MeOH) of
the residue afforded the title compound as a semi-solid
that crystallized on standing (8.8 g, 90%): mp 98–
100 °C; [h]D +4° (c 1, CHCl3); IR: w 1730 cm−1 (CO).
1H NMR (CDCl3, 200 MHz): l 3.52 (s, 6 H, OMe-3/4),
3.62 (s, 6 H, OMe-2/5), 3.98 (d, 2 H, J2,3 (4,5) 7.4 Hz,
H-3/4), 4.36 (d, 2 H, H-2/5), 9.67 (bs, 2 H, 2 COOH);
13C NMR (50 MHz): l 58.5 (OMe-2/5), 60.6 (OMe-3/
4), 80.2 (C-3/4), 81.5 (C-2/5), 174.5 (C-1/6). Anal. Calcd
for C10H18O8: C, 45.11; H, 6.81. Found: C, 44.99; H,
6.53.
1
mp 180–182 °C; IR (KBr): w 3050, 2930 (Ph) cm−1. H
NMR (CDCl3, 200 MHz): l 3.18 (s, 6 H, 2 OMe), 3.37
(s, 6 H, 2 OMe), 3.46–3.56 (m, 8 H, H-2/5, H-3/4,
H-1/6, H-1%/6%), 7.20–7.47 (m, 30 H, Ph); 13C NMR (50
MHz): l 58.3 (OMe-2/5), 60.5 (OMe-3/4), 62.5 (C-1/6),
78.8 (C-3/4), 79.1 (C-2/5), 87.0 (CꢀPh), 126.9, 127.7,
128.6, 143.9 (Ph). HRMS (FAB): [M+Na]+ found
745.3547; requires 745.3505. Anal. Calcd for C48H50O6:
C, 79.75; H, 6.97. Found: C, 79.85; H, 7.00.
3.6. 2,3,4,5-Tetra-O-methyl-D-mannitol (7)
3.9. 2,3,4,5-Tetra-O-methylgalactaric acid (10)
To a solution of 5 (10 g, 13.83 mmol) in a mixture of
Cl2H2–MeOH (30 mL) was added 10% Pd–C (3.3 g)
and the mixture was treated with H2 (45 psi) for 24 h.
The catalyst was filtered off and washed with MeOH,
and the filtrate was concentrated to a white syrup that
was purified by flash-column chromatography (20:1
Cl2H2–MeOH). The title compound was isolated as a
colorless syrup that crystallized on standing in the
refrigerator (3 g, 91%): mp 67–69 °C; [h]D +12° (c 1,
This was prepared from 8 (1.12 g, 4.70 mmol) as
described for 9. Compound 10 was obtained as a white
solid (0.9 g, 72%): mp 151–153 °C; IR: w 3066 (OH),
1
1745 (CO) cm−1. H NMR (Me2SO, 200 MHz): l 3.23
(s, 6 H, 2 OMe), 3.32 (s, 6 H, 2 OMe), 3.63 (s, 2 H, J2,3
(4,5) 0.0 Hz, H-2/5), 3.78 (s, 2 H, H-3/4), 12.65 (bs, 2
H, 2 COOH); 13C NMR (50 MHz): l 57.8 (OMe-2/5),
59.1 (OMe-3/4), 78.1 (C-3/4), 79.9 (C-2/5), 172.5 (C-1/
6). HRMS (FAB): [M+Na]+ found 289.0881; requires
289.0899. Anal. Calcd for C10H18O8: C, 45.11; H, 6.81.
Found: C, 44.93; H, 6.61.
1
CHCl3); IR:w 3442 cm−1 (OH). H NMR (CDCl3, 200
MHz): l 2.34 (s, 2 H, 2 OH), 3.30 (dt, 2 H, J1,2 (5,6) 2.5,
J1%,2
3.2, J2,3
7.7 Hz, H-2/5), 3.36 (s, 6 H,
(5,6%)
(4,5)
OMe-3/4), 3.45 (s, 6 H, OMe-2/5), 3.49 (d, 2 H, H-3/4),
3.65 (dd, 2 H, J1,1% 12.1 Hz, H-1/6), 3.92 (dd, 2 H,
H-1%/6%); 13C NMR (50 MHz): l 56.6 (OMe-2/5), 58.6
3.10. Bis(pentachlorophenyl) 2,3,4,5-tetra-O-methyl-D-
mannarate (11)
(C-1/6), 60.6 (OMe-3/4), 78.4 (C-3/4), 80.7 (C-2/5).
To a cold (0–5 °C) solution of 9 (7.2 g, 27 mmol) in dry
Cl2H2 (69 mL) were added pentachlorophenol (14.38 g,
54 mmol), N,N-dicyclohexylcarbodiimide (11.14 g, 54
mmol) and N,N-dimethylaminopyridine (87 mg). The
mixture was stirred at rt overnight, then diluted with
Cl2H2 (290 mL) and the dicyclohexylurea formed was
filtered through diatomaceus earth. The filtrate was
washed with 5% aq solution of AcOH, then with water,
dried (anhyd MgSO4) and concentrated to a white
solid, which was washed with MeOH (18.77 g, 91%):
mp 176–178 °C; [h]D +6° (c 1, CHCl3); IR: w 1781
’
HRMS (EI): [M]+ found 239.1499; requires 239.1495.
Anal. Calcd for C10H22O6: C, 50.41; H, 9.31. Found: C,
50.18; H, 9.09.
3.7. 2,3,4,5-Tetra-O-methyl-galactitol (8)
This was prepared from 6 (13.3 mg, 18.4 mmol) as
described for 7. Compound 8 was obtained as an white
solid (3 g, 69%): mp 60–62 °C; IR: w 3436 (OH) cm−1
.
1H NMR (CDCl3, 200 MHz): l 2.53 (s, 2 H, 2 OH),
3.44 (s, 6 H, 2 OMe), 3.47 (s, 6 H, 2 OMe), 3.43–3.52
(m, 4 H, H-2/5, H-3/4), 3.77 (dd, 2 H, J1,2 (5,6) 3.7, J1,1%
(6,6%) 11.7 Hz, H-1/6), 3.86 (dd, 2 H, J1%,2 (5,6%) 4.9 Hz,
H-1%/6%); 13C NMR (50 MHz): l 57.7 (OMe-2/5), 60.1
1
cm−1 (CO). H NMR (CDCl3, 200 MHz): l 3.52 (s, 6
H, OMe-3/4), 3.62 (s, 6 H, OMe-2/5), 3.98 (d, 2 H, J2,3
(4,5) 7.2 Hz, H-2/5), 4.36 (d, 2 H, H-3/4); 13C NMR (50
MHz): l 58.9 (OMe-2/5), 60.8 (OMe-3/4), 79.6 (C-3/4),
79.8 (C-2/5), 127.4–143.8 (C6Cl5), 167.5 (C-1/6).
HRMS (FAB): [M+Na]+ found 784.7617; requires
(OMe-3/4), 60.6 (C-1/6), 79.9 (C-3/4) 80.3 (C-2/5).
’
HRMS (EI): [M]+ found 239.1494; requires 239.1495.

M. Mancera et al. / Carbohydrate Research 338 (2003) 1115–1119
1119
784.7569. Anal. Calcd for C22H16O8Cl10: C, 34.63; H,
2.11. Found: C, 34.67; H, 2.20.
(C-3/4), 79.8 (C-3%/4%), 82.3 (C-2%/5%), 82.4 (C-2/5), 170.5
(C-1/6). Anal. Calcd for C20H38O10N2·0.5 H2O: C,
50.51; H, 8.27; N, 5.89. Found: C, 50.19; H 8.52; N,
5.99.
3.11. Bis(pentachlorophenyl) 2,3,4,5-tetra-O-methyl-
galactarate (12)
This was prepared from 10 (0.5 g, 1.88 mmol) as
described for 11. Compound 12 was obtained as a white
solid (0.8 g, 52%): mp 160–162 °C; IR: w 1794 (CO)
Acknowledgements
We thank the C.I.C.Y.T. (Comisio´n Interministerial
de Ciencia y Tecnolog´ıa) of Spain for financial support
(Grants MAT99-0578-C02-01 and MAT2002-04600-
C02-01).
1
cm−1. H NMR (CDCl3, 200 MHz): l 3.54 (s, 6 H,
OMe-3/4), 3.65 (s, 6 H, OMe-2/5), 4.19 (s, 2 H, J2,3 (4,5)
0.0 Hz, H-2/5), 4.42 (s, 2 H, H-3/4); 13C NMR (50
MHz): l 59.4 (OMe-2/5), 60.6 (OMe-3/4), 79.1 (C-3/4),
79.7 (C-2/5), 127.4–143.8 (C6Cl5), 167.8 (C-1/6). Anal.
Calcd for C22H16O8Cl10: C, 34.63; H, 2.11. Found: C,
34.61; H, 2.23.
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To a mixture of 11 (132 mg, 0.17 mmol) and 1,6-di-
amino-1,6-dideoxy-2,3,4,5-tetra-O-methyl- -mannitol
D
dihydrochloride5 (13; 53 mg, 0.17 mmol), under N2, dry
N-methylpyrrolidinone (2 mL) and N-ethyl-N,N-diiso-
propylamine (0.12 mL, 1.33 mmol) were added and the
mixture was stirred at 45 °C for 7 days. The reaction
mixture was diluted with dichloromethane (5 mL) and
added dropwise to Et2O (200 mL) with stirring. The
precipitated was filtered and washed with ether and
dried under diminished pressure to obtain 29 as a solid
(61 mg, 77%). Mw 31,100; Mw/Mn 1.5; Tg 67 °C (DHg
1.2 j g−1 deg−1); Tm 204 °C (DHm 65.9 j g−1); IR: w
1
3433 (NH), 1650 (amide I), 1555 cm−1 (amide II); H
NMR (CDCl3, 200 MHz): l 3.35 (s, 6 H, 2 OMe), 3.42
(s, 6 H, 2 OMe), 3.44 (s, 6 H, 2 OMe), 3.47 (s, 6 H, 2
OMe), 3.39–3.65 (m, 8 H, H-1%–6%), 3.72 (s, 2 H, J2,3
(4,5) 0.0 Hz, H-3/4), 4.09 (s, 2 H, H-2/5), 6.93 (t, 2 H,
2 NH); 13C NMR (50 MHz): l 36.9 (C-1%/6%), 56.5
(OMe), 58.0 (OMe), 60.8 (OMe), 61.3 (OMe), 78.2