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of two diastereomers the relative energy at the B3LYP/6-
311+G(d,p) and MP2/6-311+G(d,p) levels was used. All calculations
were done with GAUSSIAN 03 program.15
Epimerization of meso-lactide with potassium phosphate: To a
solution of meso-dilactide (0.7 mmol, 100 mg) in anhydrous EtOAc
(10 mL) was added K3PO4 (0.24 mmol, 50 mg). The mixture was
stirred at room temperature for 96 h, then further K3PO4
(0.09 mmol, 20 mg) was added and the mixture was stirred for
additional 72 h. The reaction was controlled by GC (on HP5 and
Lipodex E columns). Potassium phosphate was removed via centri-
fugation at 4000 rpm for 10 min. The solvent was removed in vac-
uum to yield 95 mg (95%) of stereoisomeric dilactides in a ratio of
meso:rac = 1:1.3.
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Acknowledgments
We acknowledge the financial support by Uhde GmbH Leipzig.
The authors thank Dr. C. Fisher, S. Buchholz, and S. Schareina for
excellent analytical support.
11. Jeffrey, G. A.; Saenger, W. Hydrogen Bonding in Biological Structures; Springer:
Berlin, 1991.
12. (a) n-Oct3N (pKAaN(BH+) ꢀ18), imidazole (pKAaN(BH+) ꢀ11.29), N-methyl-
Supplementary data
2 O
morpholine (NMM, pKaH = 7.4), DABCO (pKAaN(BH+) = 18.29), DBU
(pKAaN(BH+) = 24.33).
13. For a collection of all isomerization results, see Supplementary data.
14. Xu, J.; Liu, Z.-L.; Zhuo, R.-X. J. Appl. Polym. Sci. 2006, 101, 1988–1994.
15. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R.; Montgomery, Jr. J. A.; Vreven, T.; Kudin, K. N.; Burant, J. C.;
Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.;
Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.;
Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo,
C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi,
R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.;
Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe,
M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A.
GAUSSIAN 03, C. 02, Gaussian, Wallingford CT, 2004.
Supplementary data associated with this article can be found, in
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