64228-72-4Relevant academic research and scientific papers
Preparation of α-aminobenzylphosphonic acids with a stereogenic quaternary carbon atom via microscopically configurationally stable α-aminobenzyllithiums
Kuliszewska, Edyta,Hanbauer, Martin,Hammerschmidt, Friedrich
experimental part, p. 8603 - 8614 (2009/12/09)
The enantiomers of 1-phenylethylamine were phosphorylated with diethyl chlorophosphate/Et3N and then Boc-protected (Boc = tert-butoxycarbonyl) at the nitrogen atom. These phosphoramidates were metalated by using sBuLi/N,N,N′,N′-tetramethylethy-lenediamine (TMEDA) to give α-aminobenzyllithiums that isomerised to αaminophosphonates in yields of up to 80% with retention of the configuration at the carbon atom. The intermediate tertiary organolithiums were found to be microscopically configurationally stable from -78 to 0°C in Et2O. The protected a-aminophosphonates were deblocked by using boiling 6 M HCl or preferably Me3SiBr/(allyl)SiMe3. When the Boc group was replaced by the diethoxyphosphinyl group, the a-aminobenzyllithium intermediate partially enantiomerised even at -78°C and rearranged to yield an α- aminophosphonate with 50% ee (ee=enantiomeric excess). Similarly, N-Boc-protected phosphoramidates derived from racemates and/ or enantiomers of l-(1-naphthyl)ethyl-, 1-indanyl- and 1,2,3,4-tetrahydro-1-naphthylamine or 1-azidoindan- and 1-azido-1,2,3,4-tetrahydronaphthalene were converted to aminophosphonates in good yields. Deblocking gave α-aminophosphonic acids of excellent enantiomeric excess (97-99%), as determined by means of HPLC on a chiral ion-exchange stationary phase based on quinine carbamate. When racemic Boc-protected diethyl phosphoramidate derived from 1,2,3,4-tetrahydro-1- naphthylamine was metalated with LiTMP/TMEDA (TMP = 2,2,6,6- tetramethylpiperidine), 1-hydroxyethylphosphonamidates resulted. The configuration of the main isomer was determined by means of a single-crystal X-ray structure analysis.
A new and convenient asymmetric synthesis of α-amino- and α-alkyl-α-aminophosphonic acids using N-tert-butylsulfinyl imines as chiral auxiliaries
Chen, Qianyi,Yuan, Chengye
, p. 3779 - 3786 (2008/09/18)
Nucleophilic addition of dialkyl phosphites to N-tert-butylsulfinyl aldimines or ketimines occurs successfully at room temperature with potassium carbonate as base to afford α-amino- and α-alkyl-α-amino-N- (tert-butylsulfinyl)phosphonates in good to excel
