482632-06-4Relevant articles and documents
Mild, Rapid, and Chemoselective Procedure for the Introduction of the 9-Phenyl-9-fluorenyl Protecting Group into Amines, Acids, Alcohols, Sulfonamides, Amides, and Thiols
Soley, Jacob,Taylor, Scott D.
, (2020/02/04)
The 9-phenyl-9-fluorenyl (PhF) group has been used as an Nα protecting group of amino acids and their derivatives mainly as a result of its ability to prevent racemization. However, installing this group using the standard protocol, which employs 9-bromo-9-phenylfluorene/K3PO4/Pb(NO3)2, often takes days and yields can be variable. Here, we demonstrate that the PhF group can be introduced into the amino group of Weinreb's amides and methyl esters of amino acids, as well as into alcohols and carboxylic acids, rapidly and in excellent yields, using 9-chloro-9-phenylfluorene (PhFCl)/N-methylmorpholine (NMM)/AgNO3. Nα-PhF-protected amino acids can be prepared from unprotected α-amino acids, rapidly and often in near quantitative yields, by treatment with N,O-bis(trimethylsilyl)acetamide (BSA) and then PhFCl/NMM/AgNO3. Primary alcohols can be protected with the PhF group in the presence of secondary alcohols in moderate yield. Using PhFCl/AgNO3, a primary alcohol can be protected in good yield in the presence of a primary ammonium salt or a carboxylic acid. Primary sulfonamides and amides can be protected in moderate to good yields using phenylfluorenyl alcohol (PhFOH)/BF3·OEt2/K3PO4, while thiols can be protected in good to excellent yield using PhFOH/BF3·OEt2 even in the presence of a carboxylic acid or primary ammonium group.
Incorporation of (2S,3S) and (2S,3R) β-methyl aspartic acid into RGD-containing peptides
Schabbert, Silke,Pierschbacher, Michael D,Mattern, Ralph-Heiko,Goodman, Murray
, p. 3331 - 3337 (2007/10/03)
We report the synthesis and biological activity of a series of side-chain-constrained RGD peptides containing the (2S,3R) or (2S,3S) β-methyl aspartic acid within the RGD sequence. These compounds have been assayed for binding to the integrin receptors αIIbβ3 and αvβ3 and the results demonstrate the importance of the side-chain orientation of this particular residue within the RGD sequence. Based on our findings, the (2S,3S) β-methylated analogues of our RGD sequences maintain their binding potency to the integrin receptors while the (2S,3R) β-methylated analogues exhibit a drastically reduced binding affinity. Our studies demonstrate that the three-dimensional orientation of the aspartyl side chain is a very important parameter for integrin binding and that small changes that affect the side-chain orientations give rise to drastic changes in binding affinity. These results provide important information for the design of more potent RGD mimetics. Copyright
