Supporting information:
Selective polymerization of functional monomers with Novozym 435
Martijn A.J. Veld, Anja R.A. Palmans* and E.W. Meijer*
Laboratory of Macromolecular and Organic Chemistry, Technische Universiteit Eindhoven,
P.O. Box 513, 5600 MB Eindhoven, The Netherlands
* Corresponding authors. E-mail: E.W.Meijer@tue.nl and A.Palmans@tue.nl
Reactivity of isopropyl aleuriteate in Novozym 435 catalyzed reactionss
Isopropyl aleuriteate (4) contains an isopropyl ester, one primary and two secondary hydroxy
groups. Reactivity differences between the two secondary and the primary alcohol groups
were investigated by reacting 4 with a five fold excess vinyl acetate in the presence of
Novozym 435 (see Scheme SI-1a). This acyl donor results in irreversible acylation of the
alcohol groups by release of acetaldehyde and prevents the reverse reaction.1
Scheme SI-1: (a) Novozym 435 catalyzed selective acylation of isopropyl aleuriteate (4)
with vinyl acetate. (b) Novozym 435 catalyzed transesterification of -acylated isopropyl
aleuriteate (7) with benzyl alcohol.
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The reaction was monitored by means of 1H_NMR spectroscopy and the observed fractions of
acylated primary and secondary alcohol groups are shown in Figure SI-1. Upon acylation, the
position of the primary alcohol end group in 1H-NMR shifts from 3.65 ppm to 4.05 ppm.
Acylation of a secondary alcohol groups leads to new 1H-NMR signals at 4.84 ppm (multiplet
from the proton next to the acylated secondary alcohol) and 3.56 ppm (multiplet from the
proton attached to the non-acylated secondary alcohol group). Complete acylation of the
primary alcohol groups is observed within 15 minutes, whereas only 10-12% of the secondary
alcohol groups are acylated after 24 h. In a reference experiment under identical conditions
but without the addition of enzyme, some spontaneous acylation (approximately 5% after 99
h) of the primary alcohol groups of 4 was observed. No secondary alcohol acylation was
observed in this case, suggesting that the acylation of secondary alcohols observed is indeed
enzyme catalyzed.
Figure SI-1: Selectivity in the Novozym 435 catalyzed acylation of the primary () and
secondary hydroxy groups () of isopropyl aleuriteate (4).
Reactivity of both esters in -acylated isopropyl aleuriteate
For an efficient polymerization reaction of monomer 4, both the isopropyl ester and the
terminal hydroxyl group need to be reactive. To investigate the reactivity of the isopropyl
ester, -acylated isopropyl aleuriteate (7) was synthesized. Subsequently, compound 7 was
subjected to a Novozym 435 catalyzed transesterification with 3 equivalents of benzyl alcohol
at 90 °C in toluene (see Scheme SI-1b). Transesterification of the isopropyl ester results in the
formation of a benzyl ester and the release of isopropyl alcohol, while deacylation of the
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acetate ester results in the formation benzyl acetate and a free, primary hydroxy group. The
disappearance of the isopropyl ester groups (=5.00 ppm) and the formation of free primary
hydroxy groups (=3.65 ppm) were monitored by means of 1H-NMR (see Figure SI-2).
Formation of two benzylic esters (2 singlets at 5.07 and =5.08 ppm) and release of
isopropyl alcohol (heptet at =4.05 ppm) are also observed, but were more difficult to
quantify.
Figure SI-2:Transesterification of -acylated isopropyl aleuriteate (7) with 3
equivalents of benzyl alcohol. The fraction of remaining isopropyl ester groups () and
formed primary alcohol groups () are shown.
As shown in Figure SI-2, the rate at which the isopropyl ester disappears and the free primary
alcohol groups are formed are of the same order of magnitude, showing equal reactivity. After
19 h, all isopropyl ester groups have disappeared, whereas only 40% of acetate esters were
deacylated. Addition of more benzyl alcohol (7 eq) did not result in a further decrease of the
number of acylated end groups, indicating possible enzyme deactivation. More Novozym 435
(15.7 mg) was added, and a further increase (to 67%) in the number of non-acylated primary
alcohol groups was observed after an additional 3 h. The exact reason for the relatively
difficult deacylation of the acetate ester is not known. These results indicate that in an
enzymatic polymerization reaction, isopropyl aleuriteate reacts both at the primary alcohol
group and at the isopropyl ester group and will be built in into the polymer with high
selectivity.
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MALDI-TOF analysis
The sodium adducts of cyclized oligomers up to the hexamer (shown in blue in Figure SI-2)
were most abundant in the MALDI-TOF spectrum of P1. A second distribution, with a lower
intensity, was also observed and belonged to the sodium adducts of linear, isopropyl ester
terminated oligomers. Unfortunately, no information about the absolute amounts of cyclic an
linear species in P1 and P2 can be obtained from MALDI-TOF spectra, since this technique is
not quantitative and its cyclic species might be more readily ionised than linear species.2 An
identical mass distribution was obtained for polymer P2 (Cmonomer = 0.10 mmol/mL).
Figure SI-3: MALDI-TOF analysis of isopropyl aleuriteate homopolymer P1 showing two
separate mass distributions belonging to cyclic species (shown in blue) and linear isopropyl
alcohol terminated species (shown in black).
C2Na
595.83
Matrix: cyano-4-hydroxycinnamic acid
Formula repeat unit: C16H30O4
MW repeat unit: 286.21 amu
Isopropyl alcohol: 60.10 amu
Notation: [L/C][x][ion]
L: Linear, isopropyl ester terminated
C: Cyclic species
x: number of repeat units
ion: type of observed adduct
C3Na
882.12
L2Na
655.88
500
L3Na
C4Na
L5Na
L6Na
942.17
1168.42
1544.70
1800.00
L4Na
C5Na
1228.43
1455.70
1000
1500
m/z [amu]
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C6Na
1741.93
2000
Experimental
Enzymatic acylation of isopropyl aleuriteate (4) with vinyl acetate
Solid isopropyl aleuriteate (263.0 mg, 0.76 mmol) and Novozym 435 (25 mg) were put in a
Schlenk tube and dried according to the default procedure. Toluene (3.0 mL) and vinyl acetate
(350 L, 3.80 mmol) were added and the reaction mixture was directly heated under an Argon
atmosphere to 90 °C. Small aliquots (0.10 mL) were taken from the reaction mixture, filtered
over a piece of cotton in a pipette, diluted with CDCl3 and analyzed by 1H-NMR. Stirring was
continued for 115 h, after which the enzyme was filtered off over a glass filter and all
volatiles were evaporated. A pale yellow oil, which solidified upon standing, was isolated
(190 mg, 64%). 1H-NMR (CDCl3): 5.00 (h, 1H, CH(CH3)2, J = 6.3Hz), 4.05 (t, 2H,
CH2OCO, J = 6.7Hz), 3.39 (br. d, CH(OH)CH(OH), 2H, J = 5.9Hz), 2.70 (br. s., OH, 2H),
2.26 (t, 2H, CH2COO, J = 7.5Hz), 2.05 (s, CH3COO,3H), 1.68-1.55 (br. m, 4H, CH2), 1.551.45 (br. m., 2H, CH2), 1.45-1.25 (br. m, 16H, CH2), 1.23 (d, 6H, CH(CH3)2, J = 6.3Hz). 13CNMR (CDCl3):  173.59, 171.42, 74.54, 74.49, 67.49, 64.65, 34.77, 33.66, 33.58, 29.53,
29.35, 29.25, 29.09, 28.61, 25.93, 25.67, 25.65, 25.04, 21.94, 21.10.
Transesterification of -acylated isopropyl aleuriteate (7) with benzyl alcohol
-Acylated isopropyl aleuriteate (99.0 mg, 0.255 mmol) was dissolved in toluene (1.0 mL)
after which Novozym 435 (7.9 mg, not dried) and benzyl alcohol (80 L, 0.77 mmol, 3 eq.)
were added. The reaction mixture was heated to 90 oC under an Argon atmosphere. Small
aliquots (0.10 mL) were taken from the reaction mixture, filtered over a piece of cotton in a
pipette, diluted with CDCl3 and analyzed by 1H-NMR. 1H-NMR data were in agreement with
the formation of the expected reaction products: new peaks appeared at the following
positions: 1H-NMR (CDCl3): 5.10 (s, 2H, PhCH2OR), 5.08 (s, 2H, PhCH2OR), 3.61 (t, 2H,
RCH2OH, J = 6.6 Hz), 2.00 (s, CH3COO, 3H).
References
1. Wang, Y. F.; Lalonde, J. J.; Momongan, M.; Bergbreiter, D. E.; Wong, C. H. Journal of the
American Chemical Society 1988, 110, 7200-7205.
2. Lou, X. W.; van Dongen, J. L. J.; Meijer, E. W. Journal of Chromatography A 2000, 896,
19-30.
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