New Brunswick BioFlo110 Fermentor, equipped with pH and
temperature probes as well stirring rate controls. The purification
1H), 3.8 (dd, J = 3.7, 10.1 Hz, 1H), 4.21 (d, J = 17.2 Hz, 1H),
4.28 (d, J = 17.2 Hz, 1H), 4.58–4.30 (m, 5H), 7.37–7.09 (m,
10H). 13C-NMR (100 MHz, 2.5/1: CDCl3/CCl4): d ppm 70.86,
73.21, 73.53, 73.63, 75.07, 127.80, 127.93, 128.12, 128.45, 128.54,
132.75, 134.12, 204.90. HRMS for C18H20NaO4 (M + Na+): calcd.
323.1252, found: 323.1263.
of the hexa-histidine tagged enzyme was performed with an
2+
R
Ni -NTA affinity column (Invitrogenꢀ).
Preparation of benzaldehyde lyase
E.coli BL21(DE3)pLysS carrying pUC19-BALHIS construct was
used for BAL (EC. 4.1.2.38) production. The cultures were
maintained on LB agar slants. The cells from the newly prepared
slants were inoculated into the preculture Luria broth (LB)
where it was grown for 8 h at 37 ◦C, and then transferred
to the production (LB) medium with an inoculation ratio of
1/10 (1.65 L in a 2 L fermentor). 6 h after the induction with
isopropyl-b-D-thiogalactopyranoside (IPTG), cells were harvested
by centrifugation. The enzyme was either used as a crude form
without purification (the pelleted cells were transferred to a Petri
dish and lyophilized for 36 h) or as a purified enzyme.
One unit (U) of BAL activity is defined as the amount of
enzyme that catalyzes the cleavage of 1 mmol benzoin in potassium
phosphate buffer (50 mM, pH 7) containing MgSO4 (2.5 mmol
L-1), ThDP (0.15 mmol L-1), and DMSO (20 vol-%) at 30 ◦C per
minute at 30 ◦C.
(R)-3-(Benzyloxy)-1-(furan-2-yl)-2-hydroxypropan-1-one (11)
25
R
Yellow oil, [a]D : +70.3 (c 0.4, CHCl3)90% ee, Chiralpakꢀ OD
column, 98 : 2/hexane: isopropanol, 1 mL min-1, 254 nm, Rt:
68.688 min for (S), 75.499 min (R). H NMR (400 MHz, 2.5/1:
1
CDCl3/CCl4): 3.72 (dd, J = 3.26, 10.21 Hz, 1H), 3.81 (dd, J = 3.26,
10.21 Hz, 1H), 4.38 (d, J = 12.3 Hz, 1H), 4.48 (d, J = 12.3 Hz, 1H),
4.82 (t, J = 3.57 Hz, 1H), 6.47 (m, 1H), 7.06–7.09 (m, 2H), 7.11–
7.19 (m, 3H), 7.24 (d, 1H), 7.47 (m, 1H). 13C NMR (100 MHz,
2.5/1: CDCl3/CCl4): 72.26, 75.92, 95.07, 111.36, 117.70, 126, 127,
128, 137, 145.52, 145.59, 149.59, 186.32. HRMS for C14H14NaO4
(M + Na+): calcd. 269.0790, found: 269.0784.
(R)-1-(Benzyloxy)-3-hydroxy-4,4-dimethoxybutan-2-one (13)
25
R
Yellow oil, [a]D : -14.5 (c 0.4, CHCl3). 93% ee, Chiralpakꢀ OJ
column, 90 : 10/hexane: isopropanol, 0,8 mL min-1, 220 nm, Rt:
18.833 min for (S), 65.387 min (R). H-NMR (400 MHz, 2.5/1:
1
General procedure for the BAL catalyzed self condensation of
benzyloxyacetaldehyde
CDCl3/CCl4): d = 3.37 (s, 6H), 4.18 (d, J = 18.2 Hz, 2H), 4.35
(m, 2H), 4.49 (dd, J = 11.8 Hz, 1H), 4.49 (dd, J = 11.8 Hz, 1H),
7.22–7.26 (m, 5H). 13C-NMR (100 MHz, 2.5/1: CDCl3/CCl4):
d ppm 54.69, 55.971, 72.482, 72.561, 104.397, 127.009, 127.281,
127.465, 136.201, 205.274. HRMS for C13H18NaO5 (M + Na+):
calcd. 277.1052, found: 277.1045.
Benzyloxyacetaldehyde 4 (150 mg, 1 mmol) was dissolved in 10 mL
diisopropylether (25 vol-%), and then 30 mL (75 vol-%) MOPS
buffer (50mM, pH 7) containing 0.15 mM THDP and 2.5 mM
MgSO4 was added to this solution. The reaction was started with
the addition of BAL (50 U) at 30 ◦C (120 rpm). BAL was added
(50 U) on a daily basis. The reaction was monitored with TLC
and GC-MS and concluded after 96 h. The reaction mixture was
extracted with chloroform (3 ¥ 50 mL) and the combined organic
layers were dried over MgSO4, and the solvent was removed under
reduced pressure. The product was purified with flash column
chromatography.
Conclusions
BAL catalyzed the cross acyloin reactions with functionalized
acetaldehydes with the same and different protecting groups
that were achieved in high yields and enantioselectivities. All of
the products obtained in this study can be employed as chiral
synthons, as they are amenable to further modifications.
General procedure for BAL catalyzed cross condensation reactions
of benzyloxyacetaldehyde
Acknowledgements
The financial support from the Middle East Technical University,
the Scientific and Technological Research Council of Turkey
(TUBITAK), the Turkish Academy of Sciences, and the COST
CM0701 is gratefully acknowledged.
Benzyloxyacetaldehyde 4 (150 mg, 1 mmol) and the corresponding
aldehyde (1 mmol) were dissolved in 10 mL diisopropylether
(25 vol-%) then 30 mL (75 vol-%) MOPS buffer (50mM, pH 7)
containing 0.15 mM THDP and 2.5 mM MgSO4 was added to
this solution. The reaction was started with the addition of BAL
(50 U) at 30 ◦C (120 rpm). BAL was added (50 U) on a daily basis.
The reaction was monitored with TLC and GC-MS and concluded
after 96 h. The reaction mixture was extracted with chloroform (3 ¥
50 mL) and the combined organic layers were dried over MgSO4,
and the solvent was removed under reduced pressure. The product
was purified with flash column chromatography.
Notes and references
1 (a) J. L. Galman and C. H. Hailes, Tetrahedron: Asymmetry, 2009, 20,
1828–1831; (b) J. Shaeri, I. Wright, E. B. Rathbone, R. Wohlgemuth and
J. M. Woodley, Biotechnol. Bioeng., 2008, 101, 761–767; (c) Y. Kobori,
D. C. Myles and G. M. Whitesides, J. Org. Chem., 1992, 57, 5899–5907;
(d) K. Smithies, M. E. B. Smith, U. Kaulmann, J. L. Galman, J. M.
Ward and H. C. Hailes, Tetrahedron: Asymmetry, 2009, 20, 570–574;
(e) D. C. Myles, P. J. Andrulis and G. M. Whitesides, Tetrahedron Lett.,
1991, 32, 4835–4838; (f) M. E. B. Smith, B. H. Chen, E. G. Hibbert, U.
Kaulmann, K. Smithies, J. L. Galman, F. Baganz, P. A. Dalby, H. C.
Hailes, G. J. Lye, J. M. Ward, J. M. Woodley and M. Micheletti, Org.
Process Res. Dev., 2010, 14, 99–107.
(R)-1,4-Bis(benzyloxy)-3-hydroxybutan-2-one (5)
25
R
Yellowish oil, [a]D : -1.3 (c 0.9, CH2Cl2) 95% ee, Chiralpakꢀ OA
column, 80 : 20/hexane: isopropanol, 0.8 mL min-1, 220 nm, Rt:
12.036 min for (S), 13.934 min for (R).1H-NMR (400 MHz, 2.5/1:
CDCl3/CCl4): d = 3.35 (s, 1H, OH), 3.72 (dd, J = 3.7, 10.1 Hz,
2 US Pat., 0279793, 2008; US Pat., 0317342, 2009; US Pat., 0045857,
2006.
3 D. Crich, M. A. Mora and R. Cruz, Tetrahedron, 2002, 58, 35–44.
2604 | Org. Biomol. Chem., 2011, 9, 2602–2605
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