The enantiomers of 1-phenylethylamine were phosphorylated with diethyl chlorophosphate/Et(3)N and then Boc-protected (Boc=tert-butoxycarbonyl) at the nitrogen atom. These phosphoramidates were metalated by using sBuLi/N,N,N',N'-tetramethylethylenediamine (TMEDA) to give alpha-aminobenzyllithiums that isomerised to alpha-aminophosphonates 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 degrees C in Et(2)O. The protected alpha-aminophosphonates were deblocked by using boiling 6 M HCl or preferably Me(3)SiBr/(allyl)SiMe(3). When the Boc group was replaced by the diethoxyphosphinyl group, the alpha-aminobenzyllithium intermediate partially enantiomerised even at -78 degrees C and rearranged to yield an alpha-aminophosphonate with 50 % ee (ee=enantiomeric excess). Similarly, N-Boc-protected phosphoramidates derived from racemates and/or enantiomers of 1-(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 alpha-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.
Diisopropyl allyloxymethylphosphonate prepared by a one‐pot procedure was isomerized to give racemic 1‐hydroxy‐3‐butenylphosphonate with LDA by a [2,3]‐sigmatropic rearrangement. Chloroacetylation delivered an ester, which was resolved in a two‐phase system by using the lipase from Thermomyces lanuginosus. Racemic and (S)‐α‐hydroxyphosphonate 6 were converted to (±)‐ and (R)‐phosphaaspartic acid by functional‐group manipulation. (±)‐, (R)‐ and (S)‐6 were first esterified with 4‐nitrobenzenesulfonyl chloride before hydroboration to transform the double bond into a hydroxyethyl group. The hydroxyl group was manipulated to give a guanidinyl group and the 4‐nitrobenzenesulfonyloxy to give an amino group. Global deprotection of the α‐aminophosphonates yielded the desired phosphaamino acids.
A series of cationic gemini surfactants containing different spacer length were synthesized and analyzed structurally. It was shown that the surface tension (σ) and critical micelle concentration (CMC), which had a maximum for the n‐C4H8 spacer depended on the spacer length. The foaming ability and foam stability are high for the gemini surfactants with short spacers (C2H4 to n‐C4H8), while longer spacers lead to a distinct decrease of these foam parameters. Foaming properties are discussed in terms of configuration and conformation of a surfactant molecule and in relation to micellization state kinetic.
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