Written by Dr. Sharbil J. Firsan

Nitroxyl (H–N=O), the reduced form of nitric oxide (NO), a well-established biological signaling agent, is beginning to show potential as a therapeutic agent for treating heart congestion, a condition that leads to tens of thousands of deaths each year.  However, the lack of HNO-specific detection methods have hampered the study of the role it plays in biological systems.
    The study highlighted here is one attempt at developing such a detection method.  It takes advantage of the ready formation of an aza-ylide from the reaction of triphenylphosphine, tris(4,6-dimethyl-3-sulfonatophenyl)phosphine, or similar triarylphosphine with HNO in dioxane–water or in TRIS buffer.  When the aza-ylide is generated in the presence of a suitably positioned electrophilic ester group, it undergoes the Staudinger ligation to form the corresponding amide, effectively trapping HNO.

Reisz, J. A.; Klorig, E. B.; Wright, M. W.; King, S. B. Org. Lett. 2009, 11, 2719.

Written By: Matthias Junkers, Ph.D

“Staudinger Ligation: A Gift to Chemical Biology” was the title of an excellent review article published in 2004.¹
One of the outstanding applications of the Staudinger ligation depends on a class of phosphine reagents introduced simultaneously by the groups of Bertozzi and Raines in 2000. The “traceless” variant of the Staudinger ligation developed by these groups allows the formation of a native peptide bond between a thioester and an azide.^2,3
Among the suitable reagents the Raines ligation reagent diphenylphosphinemethanethiol exhibits the best reactivity profile and has already found widespread application. Two exceptional examples may highlight the potential of diphenylphosphinemethanethiol: Maarseveen and co-workers used it for intramolecular ring-closures forming medium-sized lactams.⁴ Wong and co-workers synthesized a large series of glycopeptides.⁵

Sigma-Aldrich is excited to offer acteylthiomethyl-diphenylphosphine borane complex 670359 as a convenient source for the Raines ligation reagent (Sold under license for research and development purposes only. U.S. patent 6,974,884 and related patents apply.). Obtain the active reagent easily from this shelf-stable precursor by treatment with DABCO^® at 40°C followed by basic ester cleavage.

References:
(1) “Staudinger Ligation: A Gift to Chemical Biology” Angew. Chem. Int. Ed. 2004, 43, 3106.
(2) “A ‘Traceless’ Staudinger Ligation for the Chemoselective Synthesis of Amide Bonds” Saxon, E.; Armstrong, J.I.; Bertozzi, C.R. Org. Lett. 2000, 2, 2141.
(3) “Staudinger Ligation: A Peptide from a Thioester and Azide” Nilsson, B.L.; Kiessling, L.L.; Raines, R.T. Org. Lett. 2000, 2, 1939.
(4)  “Intramolecular Staudinger Ligation: A Powerful Ring-Closure Method To Form Medium-Sized Lactams” David, O.; Meester, W.J.N.; Bieräugel, H.; Schoemaker, H.E.; Hiemstra, H.; van Maarseveen, J.H. Angew. Chem. Int. Ed. 2003, 42, 4373.
(5) “Convergent Glycopeptide Synthesis by Traceless Staudinger Ligation and Enzymatic Coupling” Liu, L.; Hong, Y.-Y., Wong, C.-H. ChemBioChem 2006, 7, 429.

Written by Matthias Junkers, Ph.D

Very often chemists have to spend more time for the tedious search of the ideal separation conditions for a chemical synthesis than the reaction itself. Through the pioneering work of Dennis P. Curran at the university of Pittsburgh light fluorous tags have become available which enable generally applicable methods for product purification orthogonal to other purification procedures. Less than a decade young these new methods enjoy a rapid increase in popularity. For a deeper look into these exciting new tools some recommendations can be made: In a recent Tetrahedron report W. Zhang and D. P. Curran give an excellent overview of synthetic applications of fluorous solid phase extraction (F-SPE).(1) Sigma-Aldrich is proud to present you its latest cheminar about “Fluorous Chemistry for Synthesis, Separation and Enrichment” which will help you to learn more about innovative new technologies and products. Access the cheminar directly via your desktop browser and enjoy the convenient navigation.

To check out Sigma Aldrich’s new Web-based chemistry seminar series, please visit sigma-aldrich.com/cheminars.

 
(1) Zhang, W.; Curran, D. P. Tetrahedron 2006, 62, 11837.

sodium tripolyphosphate
STPP
CAS NO:7758-29-4
food grade tech grade

Assay Na5P3O10   95.56
P2 O 5 %  57.08
Water Insoluble Matter %  0.03
Iron(Fe) %  100ppm
PH value (1% water solution)  9.72
Heavy Metal (as Pb) % 0.0008
Arsenic (As) %  0.0003
Fluoride (F) %  0.002
Whiteness %  91.12
density  0.81

(1) J. Prescher and C. Bertozzi, Nature Chemical Biology 2005, 13.
(2) C. Bertozzi et al., Journal of American Chemical Society 2002, 14893.
(3) C. Bertozzi et al., Angewandte Chemie International Edition 2006, 896.