PubMed · 4275894
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L Keith, A Silver, M Becker. 1974. Anesthesia for laparoscopy.. https://pubmed.ncbi.nlm.nih.gov/4275894/
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The structures of neoefrapeptins A to N, peptides with insecticidal activity, were elucidated. They showed a close similarity to efrapeptin. However, all neoefrapeptins contained the very rare amino acid 1-amino-cyclopropane-carboxylic acid and some of them also contained (2S,3S)-3-methylproline. The neoefrapeptins are the first case, in which these amino acids are found as building blocks for linear peptides. They were identified by comparison of the silylated hydrolyzate to reference material by GC/MS (EI-mode). The sequence was elucidated using mass spectrometry (ESI+ mode). Full scan spectra showed two fragments in high yield, even under mild ionization conditions. MS/MS spectra of these two fragments yielded fragment rich spectra from which the sequence of the compounds was determined almost completely. The proteolytic cleavage with the proteinase papain yielded products that allowed to prove the rest of the sequence and the identity of the C-terminus to efrapeptin. The proteolytic cleavage products allowed furthermore to determine the position of the isobaric amino acids, pipecolic acid and 3-methylproline in neoefrapeptin F, as well as the location of R-isovaline and S-isovaline. Papain digestion was such established as a tool for structure elucidation of peptides rich in alpha,alpha-dialkylated amino acids. CD spectra suggested a 3(10) helical structure for neoefrapeptins A and F.
A number of racemic 1,3-dimethyl-4-phenylpiperidines which serve as intermediates in the synthesis of opioid analgesics have been resolved on two commercially available high-performance liquid chromatography columns containing cellulose-based chiral stationary phases: Chiralcel OD and Chiralcel OJ. The resolution results were complementary between the two columns. Also, the polarity of substituents appears to play an important role on the ability of the Chiralcel OD column to resolve pairs of enantiomers.
The bromoacetals 5a and 5b react with n-butyllithium and the piperidone 7 to yield the hydroxyacetals 8b and 8c, respectively. Cyclization of 8b and 8c followed by acid hydrolysis affords the spirocyclic hemiacetals 10b and 10c which are oxidized by PCC to give the spirocyclic prodine analogues 4b and 4c. The corresponding spirocyclic pethidine derivative 2 is prepared by alkylation of the 2-benzopyran-3-one 16 with N-Lost (17). In the mouse writhing test the spiropethidine 2 is not analgesic active up to a dose of 20 mg/kg body weight (bw). In the spirocyclic prodine series the methylated lactone 4c is the most active analgesic with an ED50-value (ED50 = 9.2 mg/kg bw) in the range of the ED50-value of tramadol.