Pioneer of hyaluronan structural chemistry and other studies of polysaccharides: Torvard C. Laurent (1930–2009)

Torvard C. Laurent (1930–2009) was one of the pioneers of hyaluronan science and in particular of its structural aspects. He was the first who ever established the metrical characteristics of hyaluronan. He determined many of its physicochemical properties and their relationship to the versatile biological functions of this noted molecule. He also contributed to its medical applications. He was a leading personality in science administration and science policy in Sweden and internationally.     

Neil Bartlett and the first noble-gas compound

Neil Bartlett (1932–2008) was the first to produce non-transient amounts of a compound of a noble gas. By describing some of the circumstances of his seminal work we gain a glimpse into the process of his extraordinary experimental discovery. It happened in the spring of 1962 and was followed by an avalanche of other discoveries in noble-gas chemistry leading—over the years—to many new substances with the most interesting bonding properties and structures.     

Hermann Jahn and Rudolf Renner of the Jahn–Teller and Renner–Teller effects

Vibronic interactions have received increasing attention in modern structural chemistry. Edward Teller played a pioneering role in understanding and describing them during the “molecular physics” period of his scientific career. Very little is known about the two scientists who contributed significantly to our knowledge about these effects and whose names have become associated with Teller’s. This Editorial is devoted to Hermann Jahn and Rudolf Renner and attempts to lift them out of oblivion by paying them tribute for their contributions.

Syntheses of vinca alkaloids and related compounds. 104. A concise synthesis of (-)-vincapusine

beta-Iodo-enamines with an eburnane skeleton (5a and 5c) were obtained with the aid of iodine from compounds 2a and 2c and were then transformed into hydroxyl lactams (6a and 6c) with CuSO4.5H2O in a mixture of DMF and water. Lactams (6a and 6c) were reduced selectively with BH3.SMe2 to result in the first synthesis of (-)-vincapusine (4a) as well as its natural 14-decarbomethoxy analogue (4c).     

Method for the synthesis of multi-epitopic Streptococcus pyogenes lipopeptide vaccines using native chemical ligation

The aim of this study was to investigate methods for the synthesis of highly pure, well-characterized analogues of the lipid core peptide (LCP) system. Difficulties synthesizing and purifying conventional LCP systems have led to the requirement for a technique to produce highly pure, LCP-based vaccines for potential use in human clinical trials. The current study describes methods for the attachment of lipophilic adjuvants onto multi-epitopic peptide vaccines. Described is the synthesis, using native chemical ligation, of a highly pure, tri-epitopic, group A streptococcal (GAS) lipopeptide vaccine candidate. Intranasal immunization of the described tri-epitopic GAS lipopeptide with the mucosal adjuvant cholera toxin B subunit induced high serum IgG antibody titers specific for each of the incorporated peptide epitopes.     

Accessible Geometrical Changes

Structural Chemistry -     

On the molecular structure of (CH3)2NSO2N(CH3)2 as studied by gas electron diffraction

The following bond lengths and bond angles have been deduced from a vapour phase electron diffraction study of (CH₃)₂NSO₂N(CH₃)₂: r(C-H) 1.114 ± 0.005 Å, r(S-O) 1.432 ± 0.010 Å, r(N-C) 1.475 ± 0.013 Å, r(S-N) 1.651 ± 0.003 Å, ∠N-C-H 109.3 ± 2.0°, ∠C-N-C 118.0 ± 302°, ∠S-N-C 115.2 ± 1.1°, ∠N-S-N 110.5±1.3° and ∠O-S-O 114.7±2.5°. The sulphur bond configuration and the prevailing conformation, which was identical to that in the crystal, are discussed in relation to analogous sulphide and sulphoxide derivatives.     

Molecular structure of phenylsilane: a study by gas-phase electron diffraction and ab initio molecular orbital calculations

The molecular structure of phenylsilane has been determined accurately by gas-phase electron diffraction and ab initio MO calculations at the MP2(f.c.)/6-31G* level. The calculations indicate that the perpendicular conformation of the molecule, with a Si–H bond in a plane orthogonal to the plane of the benzene ring, is the potential energy minimum. The coplanar conformation, with a Si–H bond in the plane of the ring, corresponds to a rotational transition state. However, the difference in energy is very small, 0.13 kJ mol⁻¹, implying free rotation of the substituent at the temperature of the electron diffraction experiment (301 K). Important bond lengths from electron diffraction are: <r_g(C–C)>=1.403±0.003 Å, r_g(Si–C)=1.870±0.004 Å, and r_g(Si–H)=1.497±0.007 Å. The calculations indicate that the C_ipso–C_ortho bonds are 0.010 Å longer than the other C–C bonds. The internal ring angle at the ipso position is 118.1±0.2° from electron diffraction and 118.0° from calculations. This confirms the more than 40-year old suggestion of a possible angular deformation of the ring in phenylsilane, in an early electron diffraction study by F.A. Keidel, S.H. Bauer, J. Chem. Phys. 25 (1956) 1218.