844
D. Romano et al. / Tetrahedron: Asymmetry 16 (2005) 841–845
1,2-O-Isopropylideneglycerol formate: 1H NMR
(CDCl3, 200 MHz): 1.36 (s, 3H, CH3), 1.41 (s, 3H,
CH3), 3.68–3.76 (m, 2H, CH2), 4.01–4.18 (m, 2H,
CH2), 4.20–4.29 (m, H, CH), 8.08 (s, 1H, CHO); 1,2-
O-isopropylideneglycerol acetate: 1H NMR (CDCl3,
200 MHz): d 1.38 (s, 3H, CH3), 1.44 (s, 3H, CH3),
2.12 (s, 3H, CH3), 3.36–3.41 (m, 2H, CH2), 4.01–4.11
(m, 2H, CH2), 4.13–4.19 (m, 1H, CH); 1,2-O-isopropyl-
taken at intervals and added to an equal volume of an
internal standard solution (1-hexanol 2 g/L) in water;
the resulting solution was extracted with ethyl acetate
and analysed. The enantiomeric composition of 1,2-O-
isopropylidene glycerol, 1,2-O-isopropylidene glycerol
acetate, 1,2-O-isopropylidene glycerol propionate, 1,2-
O-isopropylidene glycerol butanoate, 1,2-O-isopropylid-
ene glycerol pentanoate, 1,2-O-isopropylidene glycerol
hexanoate and 1,2-O-isopropylidene glycerol benzoate
was determined by gas chromatographic analysis using
a chiral capillary column (diameter 0.25 mm, length
25 m, thickness 0.25 lm, DMePeBeta-CDX-PS086,
MEGA, Legnano, Italy), using the following tempera-
ture program: 10 min at 90 ꢁC, increased to 150 ꢁC over
5 min and then held at 150 ꢁC for 30 min. The retention
times of the enantiomers of 1,2-O-isopropylidene glyc-
erol and its esters under these conditions were: (R)-1,2-
O-isopropylidene glycerol = 8.2 min, (S)-1,2-O-isoprop-
ylidene glycerol = 9.0 min; (R)-1,2-O-isopropylidene
glycerol formate = 10.4 min, (S)-1,2-O-isopropylidene
glycerol formate = 9.9 min; (R)-1,2-O-isopropylidene
glycerol acetate = 13.1 min, (S)-1,2-O-isopropylidene
glycerol acetate = 12.4 min; (R)-1,2-O-isopropylidene
glycerol propionate = 17.4 min, (S)-1,2-O-isopropylid-
ene glycerol propionate = 16.4 min; (R)-1,2-O-isopropyl-
ideneglycerol
propionate:
1H
NMR
(CDCl3,
200 MHz): d 1.15 (t, 3H, CH3), 1.26 (s, 3H, CH3),
1.32 (s, 3H, CH3), 2.35 (q, 2H, CH2), 3.64–3.69 (m,
2H, CH2), 4.04–4.15 (m, 2H, CH2), 4.14–4.22 (m, 1H,
CH); 1,2-O-isopropylideneglycerol butanoate: 1H
NMR (CDCl3, 200 MHz): d 0.98 (t, 3H, CH3), 1.23–
1.36 (m, 2H, CH2), 1.29 (s, 3H, CH3), 1.38 (s, 3H,
CH3), 1.48–1.59 (m, 2H, CH2), 2.29 (t, 2H, CH2),
3.50–3.59 (m, 2H, CH2), 4.04–4.15 (m, 2H, CH2),
4.14–4.22 (m, 1H, CH); 1,2-O-isopropylideneglycerol
hexanoate: 1H NMR (CDCl3, 200 MHz): d 0.89 (t,
3H, CH3), 1.22–1.33 (m, 4H, CH2), 1.34 (s, 3H, CH3),
1.40 (s, 3H, CH3), 1.50–1.60 (m, 2H, CH2), 2.32 (t,
2H, CH2), 3.54–3.63 (m, 2H, CH2), 4.00–4.12 (m, 2H,
CH2), 4.19–4.27 (m, 1H, CH); 1,2-O-isopropylidenegly-
1
cerol phenylacetate: H NMR (CDCl3, 200 MHz): 1.32
(s, 3H, CH3), 1.41 (s, 3H, CH3), 3.40 (s, 2H, CH2),
3.48–3.56 (m, 2H, CH2), 4.08–4.15 (m, 2H, CH2),
4.11–4.24 (m, 1H, CH), 7.12–7.25 (m, 5H, Ph); 1,2-O-
isopropylideneglycerol benzoate: 1H NMR (CDCl3,
200 MHz): 1.35 (s, 3H, CH3), 1.45 (s, 3H, CH3), 3.42–
3.49 (m, 2H, CH2), 4.06–4.14 (m, 2H, CH2), 4.10–4.22
(m, 1H, CH), 7.50–8.12 (m, 5H, Ph); 1,2-O-isopropylid-
ene glycerol 4-NO2-benzoate: 1H NMR (CDCl3,
200 MHz): 1.29 (s, 3H, CH3), 1.44 (s, 3H, CH3), 3.83–
3.90 (m, 2H, CH2), 4.13–4.20 (m, 2H, CH2), 4.36–4.50
(m, 1H, CH), 8.20–8.34 (m, 4H, Ph); 1.37 (s, 3H,
CH3), 1.46 (s, 3H, CH3), 3.70 (s, 3H, OCH3), 3.79–
3.84 (m, 2H, CH2), 4.18–4.26 (m, 2H, CH2), 4.42–4.60
(m, 1H, CH), 6.70–6.81 (m, 2H, Ph), 7.79–7.86 (m,
2H, Ph).
idene
glycerol
butanoate = 22.3 min,
(S)-1,2-O-
isopropylidene glycerol butanoate = 21.2 min; (R)-1,2-
O-isopropylidene glycerol pentanoate = 25.8 min, (S)-
1,2-O-isopropylidene glycerol pentanoate = 24.9 min;
(R)-1,2-O-isopropylidene glycerol hexanoate = 30.2 min,
(S)-1,2-O-isopropylidene
29.6 min; (R)-1,2-O-isopropylidene glycerol benz-
oate = 38.2 min, (S)-1,2-O-isopropylidene glycerol
glycerol
hexanoate =
benzoate = 37.4 min. The enantiomeric composition of
4-MeO- and 4-NO2-benzoates was analysed using a
Chiralcel OD column (Daicel Chemical Industries);
the mobile phase was hexane/isopropanol (9:1) at a flow
rate of 0.5 mL minꢀ1. The retention times were:
(S)-p-MeO-benzoate 17.0 min, (R)-p-MeO-benzoate
30.1, (R)-p-NO2-benzoate 20.8 min (S)-p-NO2-benzoate
22.0 min.
3.4. Optimisation by the sequential simplex method
The simplex optimisation method was based on sequen-
tial experimental trials guided by the systematic search
strategies of the Multisimplexꢂ 2.0 program (Multisim-
plex AB, Karlskrona, Sweden).12 The starting experi-
ments were selected with levels of each control variable
(substrate concentration, pH, temperature and biomass
concentration) within the following ranges: pH 4–8,
temperature 20–26 ꢁC, substrate concentration 1–10 g/
L, biomass concentration 10–45 g/L. The control re-
sponses to be optimised were the molar conversion after
3 h and the corresponding enantiomeric ratio (E). Each
experiment was carried out in triplicate.
The absolute configurations of 1,2-O-isopropylidene
glycerol were determined by comparison with commer-
cially available enantiomerically pure samples, while
enantiomerically pure esters were synthesised starting
from enantiomerically pure 1,2-O-isopropylidene gly-
cerol following the procedure described above.
References
1. Jurczak, J.; Pikul, S.; Bauer, T. Tetrahedron 1986, 42, 447–
488.
2. Xia, J.; Hui, Y. Z. Tetrahedron: Asymmetry 1997, 8, 3019–
3021.
3. Partali, V.; Melbye, A. G.; Alvik, T.; Anthonsen, T.
Tetrahedron: Asymmetry 1992, 3, 65–72.
4. Hess, R.; Bornscheuer, U.; Capewell, A.; Scheper, T.
Enzyme Microb. Technol. 1995, 17, 725–728.
5. Bianchi, D.; Borsetti, A.; Golini, P.; Cesti, P.; Pina, C.
Tetrahedron: Asymmetry 1997, 8, 817–819.
6. Jaeger, K. E.; Schneidinger, B.; Rosenau, F.; Werner,
M.; Lang, D.; Dijkstra, B. W.; Schimossek, K.; Zonta,
3.5. Analytical methods
Alcohol and ester concentrations were determined by
gas-chromatographic (GC) analysis on a Carlo Erba
Fractovap GC gas-chromatograph equipped with a
hydrogen flame ionisation detector. The column
(3 · 2000 mm) was packed with Carbowax 1540 (10%
on Chromosorb 80–100 mesh). Samples (0.2 mL) were