REFERENCES AND NOTES
- Songster , M. F. and Barany , G. 1997 . Methods in Enzymology, Solid-Phase Peptide Synthesis Edited by: Fields , G. B. Vol. 289 , 126 – 174 . Orlando, Florida : Academic Press .
- Rabanal , F. , Giralt , E. and Albericio , F. 1995 . Tetrahedron , 51 : 1449
- Nishiuchi , Y. , Inui , T. , Nishio , H. , Bodi , J. , Kimura , T. , Tsuji , F. I. and Sakakibara , S. 1998 . S. Proc. Natl. Acad. Sci. USA , 95 : 13549
- Aviño , A. , Güimil-García , R. , Diaz , A. , Albericio , F. and Eritja , R. 1996 . Nucleos. Nucleot. , 15 : 1871
- Aviño , A. , Güimil-García , R. , Albericio , F. , Mann , M. , Wilm , M. , Neubauer , G. and Eritja , R. 1996 . Bioorgan. Med. Chem. , 4 : 1649
- de la Torre , B. G. , Albericio , F. , Saison-Behmoaras , E. , Bachi , A. and Eritja , R. 1999 . Bioconjugate Chem. , 10 : 1005 – 1012 .
- Robles , J. , Maseda , M. , Beltrán , M. , Concernau , M. , Pedroso , E. and Grandas , A. 1997 . Bioconjugate Chem. , 8 : 785 – 788 .
- Beltrán , M. , Maseda , M. , Robles , J. , Pedroso , E. and Grandas , A. 1997 . Lett. Pept. Sci. , 4 : 147
- Robles , J. , Beltrán , M. , Marchán , V. , Pérez , Y. , Travesset , I. , Pedroso , E. and Grandas , A. 1999 . Tetrahedron , 55 : 13251
- Carpino , L. A. , Chao , H. G. and Tien , J. H. 1989 . J. Org. Chem. , 54 : 4302
- Harcourt , M. P. and More O'Ferrall , R. A. 1995 . J. Chem. Soc. Perkin Trans. , 2 : 1415
- The target product may be contaminated with inorganic salts. In this case, the solid can be purified by addition of CH2Cl2 and filtration. The filtrate is evaporated to dryness and dried again over P2O5
- A high quality NaH and anhydrous conditions are crucial for the success of this reaction. Best yields are obtained when the NaH (80% suspension in paraffin oil, grey color) container is stored under moisture-free atmosphere. If it is groomy and/or has pale color (or white spots), it should not be used
- Usually, the reaction is exothermic and the temperature rises to approximately 40°C. If the temperature is higher, it can be kept at 40°C with an ice-water bath. On the other hand, if the temperature is lower and the reaction does not start, a bath with warm water can be used to maintain the temperature at ∼40°C
- If the addition is performed more rapidly and the temperature rises above 40°C, some ethyl formate (b.p. 52–54°C) may evaporate and the reaction does not go to completion
- A byproduct with an Rf value lower than the target product may appear. Preliminary spectroscopic analysis of this product indicates that it might be a byproduct derived from formylation of the carbamate nitrogen
- If the separation between both phases is not clear, the solution should be taken to a higher pH by addition of 2 N NaOH. The anionic form of the product then partitions into the aqueous phase
- If a 60% suspension of NaH in paraffin oil is used instead of an 80% suspension, a third phase is formed that does not disappear with further additions of NaOH (footnote #17). In this case TLC indicates that both the interphase and the aqueous phase contain the product, and are combined. The organic solvent is evaporated and the aqueous residue is acidified with glacial HOAc as described in the text. In this case, the product is not totally pure and may be purified by silica gel flash column chromatography eluting with CH2Cl2 and increasing amounts of CH3OH (from 0 to 5%)
- If TLC analysis shows the presence of impurities, the product may be purified by silica gel column chromatography eluting with CHCl3 and increasing amounts of CH3OH (0 to 5%)
- If HCl is totally eliminated, the subsequent precipitation does not take place properly