Juliane Keilitz et al.
FULL PAPERS
ee values were reproducible within 1%. ICP-MS measure-
ments were carried out on an Element 2 system (Thermo
Fisher) at low resolution (sample gas 0.863 LminÀ1; plasma
power 1350 Watt). Column chromatography was performed
on silica gel 60 (230–400 mesh). Hydrogenations were car-
ried out in an autoclave from Roth equipped with a magnet-
ic stirrer. Ultrafiltration was performed with a 300-mL sol-
vent-resistant stirred cell with regenerated cellulose mem-
branes (molecular weight cut-off 5000, 10000 gmolÀ1), both
from Millipore. Ethyl and methyl pyruvates were freshly dis-
tilled prior to use. All other reagents and solvents were pur-
chased from Acros, Fluka or Aldrich and used as received.
The general synthesis of double- and single-shell building
blocks (mPEGy-CnÀ1-COOH and mPEGy-COOH) as well as
core-shell polymers (hPGx-Cn-mPEGy and hPGx-mPEGy)
will be described elsewhere, including analytical data for
CH2CH2CONH
ACHTUNGTRNE(NUNG hPG), CH2CH2CONH], 1.55 [m, 4H,
CH2CH2CONHACTHNUGTRENUN(G hPG), CH2CH2CONH], 1.18 [m, 24H,
-(CH2)12-]; 13C NMR (100 MHz, CDCl3): d=173.4, 71.8,
71.0–69.4, 58.9, 39.0, 36.5, 29.8–28.7, 25.7; IR (KBr): n=
3303, 2918, 2851, 2100, 1642, 1553, 1466, 1349, 1251,
1111 cmÀ1; GPC: Mn =117000 gmolÀ1, Mw =261700 gmolÀ1.
Synthesis of Pt Nanoparticles in Core-Shell Polymers
Aqueous stock solutions of polymer (10.0 mg/mL) and
H2PtCl6·6H2O (various concentrations) were prepared and
combined according to the desired Pt/metal ratio. The
volume was filled up to 500 mL (overall 1 mg Pt/mL) with
water and left at room temperature for 24 h. 500 mL of a
freshly prepared aqueous NaBH4 solution (containing
3 equiv. NaBH4 according to Pt) were added at once, upon
which the solution turned dark brown to black. After anoth-
er 24 h at room temperature the water was removed under
vacuum and appropriate solvent was added.
mPEG750-C17-COOH, hPG3000-C18-mPEG750 and hPG3000
-
mPEG750
.
Double Shell Building Blocks
Hydrogenation Procedure
mPEG350-C11-COOH: Yield: 91%. 1H NMR (400 MHz,
CDCl3): d=6.30 (m, 1H, NH), 3.70–3.32 (m, PEG-back-
bone), 3.32 (s, 3H, mPEG-OMe), 2.25 (t, 2H,
CH2CH2COOH), 2.13 (t, 2H, CH2CH2CONH), 1.56 (m, 4H,
CH2CH2COOH, CH2CH2CONH), 1.22 [m, 12H, -(CH2)6-];
13C NMR (100 MHz, CDCl3): d=177.4, 173.5, 71.7, 70.4,
70.3, 70.0, 69.7, 58.8, 39.0, 36.4, 33.9, 29.2–28.7, 25.5, 24.6; IR
(KBr): n=3336, 2925, 2857, 1727, 1649, 1550, 1457, 1350,
1287, 1249, 1199, 1106 cmÀ1.
The catalyst was dissolved in the appropriate solvent and
the respective amount of chiral alkaloid in acetic acid
(0.1 mmol/mL) was added. The mixture was stirred for 2 h,
ethyl pyruvate (285 mL, 2.6 mmol, S/C 1000/1) or methyl
pyruvate (232 mL, 2.6 mmol, S/C 1000/1) was added and the
homogeneous mixture was conducted to hydrogenation for
1 hour. A sample was taken, filtered through a small plug of
silica gel with ethyl acetate and subjected to GC analysis.
Ethyl pyruvate: conversion: test column, flow
0.7 mLminÀ1, 40 to 708C with 108CminÀ1, hold 1 min, to
1008C with 208CminÀ1; ethyl pyruvate 2.95 min, ethyl lac-
tate 3.12 min; enantiomeric excess: chiral column, flow
2.5 mLminÀ1, 40 to 1008C with 108CminÀ1; (R)-ethyl lactate
3.96 min, (S)-ethyl lactate 4.17 min.
mPEG750-C11-COOH: Yield: 91%. 1H NMR (400 MHz,
CDCl3): d=6.25 (m, 1H, NH), 3.70–3.33 (m, PEG-back-
bone), 3.30 (s, 3H, mPEG-OMe), 2.22 (t, 2H,
CH2CH2COOH), 2.10 (t, 2H, CH2CH2CONH), 1.53 (m, 4H,
CH2CH2COOH, CH2CH2CONH), 1.19 [m, 12H, -(CH2)6-];
13C NMR (100 MHz, CDCl3): d=177.0, 173.4, 71.7, 70.6,
70.5–69.3, 58.7, 38.9, 36.3, 33.8, 29.1–28.7, 25.4, 24.5; IR
(KBr): n=3506, 3362, 2921, 2889, 1728, 1651, 1541, 1456,
1349, 1297, 1249, 1199, 1107, 949 cmÀ1.
Methyl pyruvate: chiral column, flow 2.5 mLminÀ1, 40 to
808C with 108CminÀ1; methyl pyruvate 3.50 min, (R)-methyl
lactate 4.25 min, (S)-methyl lactate 4.45 min.
Recycling via Ultrafiltration
Double Shell Polymers
:
Yield: 51%. 1H NMR (400 MHz,
The catalyst with 3 mg Pt nanoparticles in water/acetic acid
(1/1, 6 mL) was modified with cinchonidine (catalyst/modifi-
er 1/1.5) and ethyl pyruvate (1710 mL, 15.4 mmol, S/C 1000/
1) was added. After hydrogenation at 70 bar the mixture
was diluted with methanol, transferred to the ultrafiltration
cell and 3–5 filtration cycles were performed until the cata-
lyst is removed from the cell, dried under vacuum and redis-
solved in water/acetic acid before the next run was per-
formed.
hPG6000-C12-mPEG350
CDCl3): d=6.48 (br s, NH), 3.80–3.32 (m, hPG- and PEG-
backbone), 3.34 (s, 3H, mPEG-OMe), 2.13 [t, 4H,
CH2CH2CONHACHTUNGTRENNUNG(hPG), CH2CH2CONH], 1.55 (m, 4H,
CH2CH2COOH, CH2CH2CONH), 1.22 [m, 12H, -(CH2)6-];
13C NMR (100 MHz, CDCl3): d=173.4, 71.8, 71.4–69.0, 58.9,
39.0, 36.5, 29.5–28.7, 25.7; IR (KBr): n=3289, 3077, 2924,
2857, 2100, 1648, 1546, 1458, 1350, 1250, 1104 cmÀ1; GPC:
Mn =75700 gmolÀ1, Mw =91400 gmolÀ1.
hPG6000-C12-mPEG750: Yield: 56%. 1H NMR (400 MHz,
CDCl3): d=3.85–3.35 (m, hPG- and PEG-backbone), 3.34
(s, 3H, mPEG-OMe), 2.13 [m, 4H, CH2CH2CONH
ACHTUNGTRNE(NUNG hPG),
CH2CH2CONH], 1.56 [m, 4H, CH2CH2CONH(hPG),
AHCTUNGTRENNUNG
CH2CH2CONH], 1.24 [m, 12H, -(CH2)6-]; 13C NMR
(100 MHz, CDCl3): d=175.8, 173.5, 71.8, 71.6–69.4, 58.9,
39.0, 36.5, 29.6–28.4, 25.7; IR (KBr): n=3304, 3072, 2923,
2865, 2100, 1718, 1654, 1648, 1544, 1458, 1349, 1250,
1107 cmÀ1. GPC: Mn =87200 gmolÀ1, Mw =136100 gmolÀ1.
hPG6000-C18-mPEG750. Yield: 45%. 1H NMR (400 MHz,
CDCl3): d=6.43 (br s, NH), 3.90–3.33 (m, hPG- and PEG-
backbone), 3.32 (s, 3H, mPEG-OMe), 2.11 [t, 4H,
Acknowledgements
The authors thank Cognis GmbH (Germany) for a donation
of octadecanedioic acid. We acknowledge Dipl.-Ing. Thomas
Wons for ICP-MS measurements, Andrea Schulz and Wiebke
Fischer for TEM measurements and thank Stephen Schrettl
and Cathleen Schlesener for technical assistance. This work is
part of the Cluster of Excellence “Unifying Concepts in Cat-
1510
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 1503 – 1511