Macromolecules, Vol. 36, No. 11, 2003
Copolymerization of Chiral Acetylenes 3939
Sch em e 1
The present study deals with the copolymerization of
L-1A with the optical isomer, D-1A, and achiral mono-
mers, hexanoic acid N-propargylamide (2A), and pivalic
acid N-propargylamide (3A), and analysis of the chi-
roptical properties of the copolymers.
Exp er im en ta l Section
Mea su r em en ts. 1H and 13C NMR spectra were recorded
in chloroform-d (CDCl3) on a J EOL EX-400 spectrometer. IR
spectra were measured using a Shimadzu FTIR-8100 spectro-
photometer. The number- and weight-average molecular weights
(Mn and Mw) of polymers were determined by gel permeation
chromatography (GPC) on a J asco Gulliver system (PU-980,
CO-965, RI-930, and UV-1570) equipped with polystyrene gel
columns (Shodex columns K804, K805, and J 806), using THF
as an eluent at a flow rate of 1.0 mL/min, calibrated by
polystyrene standards at 40 °C. CD and UV-vis spectra were
recorded in a quartz cell (thickness: 1 cm) at room tempera-
ture using a J asco J 600 or J 800 spectropolarimeter and a
Shimadzu UV-2200 spectrophotometer, respectively. Melting
points (mp) were measured on a Yanaco micro melting point
apparatus. Specific rotations ([R]D) were measured on a J asco
DIP-1000 digital polarimeter with a sodium lamp as a light
source.
Ma ter ia ls. CH2Cl2 was distilled by the standard procedures.
All the reagents in monomer synthesis were used as purchased
without purification. (nbd)Rh+[η6-C6H5B-(C6H5)3] was pre-
pared by the reaction of [(nbd)RhCl]2 with NaB(C6H5)4 as
described in the literature.19 L-1A and hexanoic acid N-
propargylamide (2A) were synthesized according to our previ-
ous method.17c,18
Syn th esis of N-(ter t-Bu toxyca r bon yl)-D-a la n in e N′-
P r op a r gyla m id e (D-1A). Di-tert-butyl dicarbonate (24 g, 0.11
mol) was added to a solution of D-alanine (8.91 g, 0.10 mol)
and triethylamine (14 mL, 0.10 mol) in 1,4-dioxane/H2O
(volume ratio: 1/1, 100 mL) at 0 °C, and the resulting mixture
was stirred at room-temperature overnight. It was washed
with AcOEt (100 mL). 5 N HCl was added to the solution to
adjust its pH at 2, and then AcOEt (100 mL) was added to
the solution. The organic layer was washed with saturated
aqueous sodium chloride, dried over anhydrous Na2SO4, and
concentrated by rotary evaporation. The residue was purified
by recrystallization from AcOEt to obtain solid N-tert-butoxy-
carbonyl-D-alanine (Boc-D-alanine) in 75% yield. D-1A was
prepared from Boc-D-alanine and propargylamine in a manner
similar to l-1A in 62% yield. Mp: 137 °C. [R]D 50.7 ° (c ) 1.00
g/dL, in CHCl3 at room temperature). 1H NMR (400 MHz,
CDCl3): δ 1.37-1.38 (m, 3H, CH3), 1.45 [s, 9H, (CH3)3], 2.23
(s, 1H, CtCH), 4.04 (s, 2H, CH2), 4.17 (s, 1H, H3CCHNH), 4.96
(s, 1H, NHCOO), 6.51 (s, 1H, NHCO). 13C NMR (100 MHz,
CDCl3): δ 18.24 (CH3), 28.26 [(CH3)3], 29.07 (CH2), 49.81
(H3CCH), 71.46 [C(CH3)3], 79.31 (HCt), 80.22 (HCtC), 155.57
(NHCOO), 172.46 (CONH). IR (cm-1, KBr): 3360 (N-H), 3297
(H-Ct), 2963, 3045, 2980, 2973, 2932, 1675 (CdO), 1550 (N-
H, C-N), 1453, 1389, 1368, 1302, 1266, 1229, 1175, 1123, 1080,
1040, 1024, 932, 874, 787, 756, 743, 693, 664, 617, 586, 524.
Anal. Calcd for C11H18N2O3: C, 58.37; H, 8.02; N, 12.38.
Found: C, 58.25; H, 7.84; N, 12.50.
was added to (nbd)Rh+[η6-C6H5B-(C6H5)3] (10.6 mg, 0.02
mmol), and the resulting mixture was vigorously stirred. It
was kept in a water bath at 30 °C for 1 h. Then, acetic acid
(30 µL) was added to the reaction mixture. The resulting
mixture was poured into n-hexane (200 mL) to precipitate a
copolymer. It was separated by filtration using a membrane
filter (ADVANTEC H100A047A), and dried under reduced
pressure. Yield: 210 mg (93%).
Sp ectr oscop ic Da ta of th e P olym er s. P oly(D-1A). 1H
NMR (400 MHz, CDCl3): δ 1.41 [br s, 12H, CH3, (CH3)3], 4.15
(br s, 3H, CHCH3, CH2), 5.70 (br s, 1H, NH), 6.16 (br s, 1H,
-CHdC), 6.60 (br s, 1H, NH). 13C NMR (100 MHz, CDCl3): δ
19.38 (CH3), 28.46 [(CH3)3], 50.35 (CHCH3), 79.23 (CH2), 125.50
(HCd), 137.70 (dCCH2), 155.22 (NHCOO), 175.57 (NHCO).
IR (cm-1, KBr): 3310 (N-H), 2980, 2936, 1670 (CdO), 1520
(N-H, C-N), 1460, 1393, 1368, 1252, 1169, 1026.
P oly(L-1A0.50-co-D-1A0.50). 1H NMR (400 MHz, CDCl3): δ
1.46 [br s, 12H, CH3, (CH3)3], 4.37 (br s, 3H, CHCH3, CH2),
6.15 (br s, 1H, -CHdC), 7.92 (br s, 1H NH). 13C NMR (100
MHz, CDCl3): δ 19.41 (CH3), 28.70 [(CH3)3], 44.81 [C(CH3)3],
50.32 (CHCH3), 79.76 (CH2), 126.49 (HCd), 136.93 (dCCH2),
155.80 (NHCOO), 174.33 (NHCO). IR (cm-1, KBr): 3320 (N-
H), 2980, 2936, 1670 (CdO), 1520 (N-H, C-N), 1460, 1393,
1368, 1250, 1050, 1026, 854.
P oly(L-1A0.50-co-2A0.50). 1H NMR (400 MHz, CDCl3): δ 0.88
(br s, CH3 of 2A), 1.31 (br s, CH2 of 2A), 1.42 [br s, CH3 and
(CH3)3 of L-1A], 1.60 (br s, CH2 of 2A), 2.24 (br s, CH2 of 2A),
3.93 (br s, COCH2 of 2A), 4.24 (br s, CH2 of L-1A), 6.09 (br s,
NH of L-1A and 2A), 7.82 (br s, NH of l-1A). 13C NMR (100
MHz, CDCl3): δ 13.91 (CH3 of 2A), 19.08 (CH3 of L-1A), 22.39,
25.78 (CH2 of 2A), 28.39 [(CH3)3 of L-1A], 29.12, 31.50, 36.13
(CH2 of 2A), 44.80 [C(CH3)3 of L-1A], 50.61 (CHCH3 of L-1A),
79.43 and 79.58 (CH2 of L-1A and 2A), 125.77 (HCd of L-1A
and 2A), 136.33 and 137.22 (dCCH2 of L-1A and 2A), 155.33
(NHCOO of L-1A), 173.95 and 174.60 (NHCO of L-1A and 2A).
IR (cm-1, KBr): 3310 (N-H), 3090, 2975, 2940, 2850, 1650
(CdO), 1540 (N-H, C-N), 1453, 1380, 1368, 1250, 1057, 1024,
857.
Syn th esis of P iva lic Acid N-P r op a r gyla m id e (3A). The
title compound was synthesized from pivalic acid instead of
Boc-L-alanine in a manner similar to L-1A in 50% yield. Mp:
66.5-67.0 °C. 1H NMR (400 MHz, CDCl3): δ 1.20-1.29 [m,
9H, C(CH3)3], 2.24 (s, 1H, HC≡), 3.99-4.10 (m, 2H, CH2), 5.89
(s, 1H, NH). 13C NMR (100 MHz, CDCl3): δ 27.70 [C(CH3)3],
29.65 (CH2), 38.89 [C(CH3)3], 71.75, 71.86 (HCt), 80.09 (HCt
C), 178.35 (NHCO). IR (cm-1, KBr): 3320 (H-Ct), 2969, 2360
(CtC), 1642 (CdO), 1530 (N-H, C-N), 1480, 1366, 1352,
1298, 1264, 1227, 1211, 1010, 627, 559. Anal. Calcd for
P oly(L-1A0.50-co-3A0.50). 1H NMR (400 MHz, CDCl3): δ 1.16
(br s, (CH3)3 of 3A), 1.41 [br s, CH3, (CH3)3 of L-1A], 1.60 (br s,
CH2 of 3A), 2.18 and 4.75 (br s, CH2 of L-1A and 3A), 6.08 (br
s, NH of L-1A and 3A). 13C NMR (100 MHz, CDCl3): δ 19.52
(CH3 of L-1A), 27.99 [(CH3)3 of l-1A], 28.74 [(CH3)3 of 3A], 50.39
and 51.09 [C(CH3)3 of L-1A and 3A], 79.58 and 79.84, (CH2 of
L-1A and 3A), 125.80 (HCd of L-1A and 2A), 138.63 (dCCH2
of L-1A and 3A), 155.13 (NHCOO of L-1A), 178.30 and 180.00
(NHCO of L-1A and 3A). IR (cm-1, KBr): 3320 (N-H), 2979,
2920, 1610 (CdO), 1520 (N-H, C-N), 1458, 1368, 1250, 1169.
C
12H20N2O3: C, 59.98; H, 8.39; N, 11.66. Found: C, 59.99; H,
8.11; N, 11.59.
Cop olym er iza tion (Typ ica l P r oced u r e). All the poly-
merizations were carried out in a Schlenk tube equipped with
a three-way stopcock under nitrogen. A solution of L-1A (113
mg, 0.5 mmol) and D-1A (113 mg, 0.5 mmol) in CH2Cl2 (5 mL)
Resu lts a n d Discu ssion
Mon om er Syn th esis. Scheme 1 illustrates the syn-
thetic routes for the monomers used, L-1A, D-1A, 2A,