195244-96-3Relevant academic research and scientific papers
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.
Enantiospecific Synthesis of N-9-Phenylfluoren-9-yl-α-amino Ketones
Paleo, M. Rita,Calaza, M. Isabel,Sardina, F. Javier
, p. 6862 - 6869 (2007/10/03)
Enantiomerically pure N-(9-phenylfluoren-9-yl)-α-amino ketones were prepared in excellent yields by acylation of organolithium reagents with N-(9-phenylfluoren-9-yl)-α-amino acid-derived oxazolidinones. The method is not applicable for the acylation of Grignard reagents as they attack the methylenic carbon of the oxazolidinone to give the corresponding N-alkylated amino acids 13 in excellent yields. The resulting N-(9-phenylfluoren-9-yl)-α-amino ketones 8 could be stereoselectively reduced to the corresponding syn- or anti-β-amino alcohols depending upon the nature of the reducing agent.
