The synthesis and characterization of chiral fluorinated analogues of norvaline and norleucine from commercially available starting materials are presented. Full experimental details for the synthesis of the following amino acids are given: (S)-4,4-difluoronorvaline, (S)-4,4,5,5,5-pentafluoronorvaline, (S)-5,5-difluoro-norleucine, (S)-5,5,6,6,6-pentafluoronorleucine, and (S)-4,4,5,5,6,6,6-heptafluoro-norleucine. These compounds were prepared with a view to obtaining new amino acids which possess physical and chemical properties so that their principal properties would be outside the range of variation of hitherto known amino acids. The principal properties are determined as latent variables in principal component analysis of molecular property descriptors. Two of the fluorinated amino acids, (S)-5,5,6,6,6-pentafluoronorleucine and (S)-4,4,5,5,6,6,6-heptafluoronorleucine were found to have principal properties outside the variation of previously characterized natural and synthetic amino acids. The principal properties, z parameters, for the five new fluorinated amino acids are given.

Protonation constants of four isopropyl esters of clodronic acid were determined by P-31-NMR and potentiometric measurements in aqueous solution at 25-degrees-C and I = 1.0 (Me4NCl). The compounds studied were monoisopropyl clodronate trisodium salt, P,P-diisopropyl clodronate disodium salt, P,P'-diisopropyl clodronate disodium salt and triisopropyl clodronate monosodium salt. All these esters are rather acidic; the first proton dissociates at pH < 1.5. P-31 NMR data of monoisopropyl and P,P-diisopropyl ester gave evidence of the formation of the cyclic structure in protonation.

The electron diffraction pattern of Sb(CH3)5 recorded with an all-glass inlet system at room temperature confirms the trigonal bipyramidal structure and yields the bond distances Sb-C(eq) = 214.0(5) pm and Sb-C(ax) = 226.4(11) pm. C-13 NMR spectra in CD2Cl2 contain only one line which remains sharp down to -90-degrees-C. The molecule presumably undergoes Berry pseudorotation over a square pyramidal transition state which leads to rapid exchange of axial and equatorial methyl groups. Trigonal bipyramidal and square pyramidal models of Sb(CH3)5 were optimized at the SCF MO level. Electron correlation was included with the modified coupled pair functional (MCPF) method. The calculations at this level suggest that the energy of the trigonal bipyramidal configuration is 7.1 kJ mol-1 below the energy of the square pyramidal configuration. Similar calculations on the unknown compound Bi(CH3)5 suggest that this molecule too would have an trigonal bipyramidal equilibrium configuration.

A procedure is given for the preparation of fac- [Ir(tacn)Cl3] (tacn = 1,4,7-triazacyclononane) from the iridium(III) alum, and a straightforward method for synthesis of Cs[lr(H2O)6](SO4)2 . 6H2O in good yield is also given. The crystal structure of fac- [Ir(tacn)Cl3] was determined by single-crystal X-ray diffraction (orthorhombic, Pna21, a = 12.0487(15), b = 7.969(2), c = 16.9735(11)angstrom, Z = 4).

Chemischer InformationsdienstVolume 17, Issue 26 Physical Organic Chemistry ChemInform Abstract: Vibrational Spectra and Force Constants of W(OCH3)6, Mo(OCH3)6, and [Sb(CH3)4][Sb(OCH3)6]. G. TATZEL, G. TATZELSearch for more papers by this authorM. GREUNE, M. GREUNESearch for more papers by this authorJ. WEIDLEIN, J. WEIDLEINSearch for more papers by this authorE. JACOB, E. JACOBSearch for more papers by this author G. TATZEL, G. TATZELSearch for more papers by this authorM. GREUNE, M. GREUNESearch for more papers by this authorJ. WEIDLEIN, J. WEIDLEINSearch for more papers by this authorE. JACOB, E. JACOBSearch for more papers by this author First published: July 1, 1986 https://doi.org/10.1002/chin.198626044AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue26July 1, 1986 RelatedInformation

AbstractDie IR‐ und Ramanspektren der monomeren Hexamethoxide des Wolframs und Molybdäns sowie des ionischen [Me4Sb]+[Sb(OMe)6]− (dargestellt aus [Sb(OMe)5]2 und Me4SbOMe; Me = CH3) werden aufgenommen und der Punktgruppe C3i zugeordnet. Kraftkonstantenrechnungen für W(OMe)6 und für [Sb(OMe)6]− ergeben praktisch identische WO‐ und SbO‐Valenzkraftkonstanten (2,56 N/cm), dagegen sind die übrigen Kraftkonstanten signifikant verschieden.