References
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- It has been repeatedly observed that the intensity of the spot on a TLC plate corresponding to the starting acceptor diminishes only to a certain point as the glycosylation reaction progresses. Beyond this point, addition of more glycosylation agent, or prolonged reaction time, does not diminish the intensity of this spot any further. The reason for this apparently mysterious behaviour is that the original acceptor has undergone a reaction, products of which by chance have the same Rf as the starting material. The cited benzoyl migration is an example of such misleading TLC behaviour.
- Urban , F. J. , Moore , B. S. and Breitenbach , R. 1990 . Tetrahedron Lett. , 31 : 4421
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- Typical conditions: The alcohol (2 mMol), the imidate (2.6 Mmol) and AgOTF (2.6 mMol) were dried in the dark in a RB flask at high vacuum. Note that the best yields are obtained without molecular sieves or added base. The flask was opened to argon and dichloromethane (10 mL) was added and the reaction left to stir at room temperature in the dark. When TLC of the reaction mixture indicated that the reaction was complete (24–48 h) the mixture was added directly to a flash silica gel column and eluted with the appropriate solvent mixture. Values of [α]D, ΔH and ΔC were measured in CHCl3 or CDCl3 at 22 °C, III:[α]D +32.7 (c 0.83); 1H (500 MHz) 5.459 d J12 8.1 H1 GalNAc; 4.571 d J12 7.7 H1 Gal; 3.379 s OCH3; 2.164, 1.970, 1.814 3 × s COCH3: 13C 101.4 Cl GalNAc; 97.8 Cl Gal; FAB-MS Obs. MH+ 946.2516 Calcd. for C48H45018N Na 946.2534.
- Paulsen , H. and Helpap , B. 1991 . Carbohydr. Res. , 216 : 289
- Douglas , S. P. and Krepinsky , J. J. In Preparation
- Values of [α]D, ΔH and ΔC were measured in CHCl3 or CDCl3 at 22 °C, VIa:[α]D +24.8° (c 0.7); 1H (500 MHz) 4.546 d J12 1.0 H1 ß-Man; 4.961 d J12 3.8 H1 α-GlcNAc; 4.467 d J12 7.8 H1 ß-Gal; 4.253 d J12 7.8 ß-GlcNAc; 5.082 d J12 2.0 H-l α-Man; 13C 101.21 CI ß-Man; 97.10 CI α-GlcNAc; 101.16 CI ß-Gal; 100.63 CI ß-GlcNAc; 98.59 α-Man; FAB-MS Obs. [M-HOCH2Ph]+ 1579.5739 Calcd. for. C76H95O34N2 1579.5765.
- Silwanis , B. A. , El-Sokkary , R. I. , Nashed , N. A. and Paulsen , H. 1991 . J. Carbohydr. Chem. , 10 : 1067 b) M. Trumtel, P. Tavecchia, A. Veyrières, P. Sina, Carbohydr. Res. 191, 29 (1989).
- Values of [α]D and ΔH were measured in CHCl3 or CDCl3 at 22 °C, VIII:[α]D +28.5 (c 0.27); 1H (500 MHz) 4.238 brs J12 <0.5 HI ß-Man; 2.607 ddd J45 10.0, J56 3.2, J56. <1 H5 ß-Man; 4.916 d J12 3.8 HI α-GlcNAc; 4.509 d J12 8.5 HI ß-Gal; 5.065 d J12 7.5 ß1,2-GlcNAc; 4.666 brs J12 <0.5 H-l α-Man; 5.298 d J12 8.5 HI ß1,4-GlcNPhth; 5.793 dd J23 10.8, J34 8.7 H3 GlcNPhth; FAB-MS Obs. MH+ 2106.7600 Calcd. for. C103H124O44N3 2106.7557.
- Tang , T. H. , Whitfield , D. M. , Douglas , S. P. , Csizmadia , I. and Krepinsky , J. J. Can. J. Chem. , 70 In Press; D. M. Whitfield, T. H. Tang, S. P. Douglas, I. Csizmadia, F. L. Moolten, J. J. Krepinsky, In Preparation