Infrared spectra of acetylated and benzoylated glycopyranosyl fluorides

Summary Infrared spectra of a number of acetylated and benzoylated glycopyranosyl fluorides have been taken. It has been observed that, with a single exception, compounds in which the fluorine atom is axially bound absorb in the region 748–802 cm^–1 whereas compounds with an equatorially bound fluorine atom show no absorption in this region. The infrared spectra may be used to assign the anomeric configuration of glycopyranosyl fluorides if their conformation is known.

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Zusammenfassung Die IR-Spektren einiger acetylierter und benzoylierter Glykopyranosylfluoride wurden aufgenommen. Dabei wurde beobachtet, daß alle Verbindungen mit axial gebundenem Fluor mit einer einzigen Ausnahme in dem Gebiet 748 bis 802 cm^–1 absorbieren, während Verbindungen mit äquatorial gebundenem Fluor in diesem Gebiet keine Absorption zeigen. Die IR-Spektren können daher zur Feststellung der anomeren Konfiguration solcher Verbindungen dienen, soferne deren Konformation bekannt ist.

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Résumé On a enregistré le spectre infrarouge d'un certain nombre de fluorures de glycopyranosyles acétylés et benzoylés. On a observé, à une seule exception près, que les composés dans lesquels l'atome de fluor est lié axialement absorbent dans la région 748–820 cm^–1, tandis que ceux où le fluor est lié équatorialement ne montrent pas d'absorption dans cette région. On peut utiliser les spectres d'absorption infrarouge pour déterminer la configuration anomère des fluorures de glycopyranosyle si leur conformation est connue.

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Dedicated to Prof. Dr. Ing.M. Jureek on the occasion of his 60th birthday.

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The authors are indebted to cand. pharmI. Krogh Andersen for the infrared spectra. Microanalyses were made by Mr.Preben Hansen.     

Poly(2‐oxazoline)‐derived Contact Biocides: Contributions to the Understanding of Antimicrobial Activity

A set of poly(2‐oxazoline)‐derived (co‐)polymers was prepared by microwave‐assisted polymerizations and acid‐mediated hydrolysis and tested for antimicrobial activity in 50 × 50 × 2 mm PP compound plates containing 5 wt% of the polymers. Antimicrobial activity against gram‐negative E. coli and P. aeruginosa as well as C. albicans depended only on the degree of hydrolysis, while antimicrobial activity against gram‐positive S. aureus was only observed for hydrolyzed poly(2‐nonyl‐2‐oxazoline)s. The surface energies of the compound plates compared to pure PP were hardly altered, and the compounds can be considered as alternatives for PP. The presence of the biocide additives at the surface of the PP compound plates could be shown by combined ATR‐IR, zeta potential, and SEM‐EDX measurements. Antimicrobial activity was maintained during double incubation as well as for lowered amounts of the biocide additive of 1% in PP compound plates.

     

Straightforward synthesis of cholic acid stabilized loop mimetics

We here report on a new straightforward strategy for the synthesis of cyclic cholic acid–peptide conjugates. A solid-phase synthesis method is presented in which a selected anti-lysozyme CDR3 fragment, Asp-Ser-Thr-Ile-Tyr-Ala-Ser-Tyr-Tyr-Glu-Ser, is immobilized onto a steroidal cholic acid derived scaffold in order to yield a loop-like structure. Therefore, part of the desired sequence, that is, Ser-Tyr-Tyr-Glu-Ser, is introduced, at the C12 position of the scaffold. Subsequently, the remainder of the envisaged sequence is introduced at C3 via a Cu-catalyzed cyclo-addition reaction. Finally, amide bond formation delivers the desired cyclic peptidosteroid. This new synthetic strategy offers an easy and short access to cyclic peptidosteroids via convergent peptide ligation and macrocyclization.     

Effects of envelope shape on interaural envelope delay sensitivity in acoustic and electric hearing

The envelope shape is important for the perception of interaural time difference (ITD) in the envelope as supported by the improved sensitivity for transposed tones compared to sinusoidally amplitude-modulated (SAM) tones. The present study investigated the effects of specific envelope parameters in nine normal-hearing (NH) and seven cochlear-implant (CI) listeners, using high-rate carriers with 27-Hz trapezoidal modulation. In NH listeners, increasing the off time (the silent interval in each modulation cycle) up to 12 ms, increasing the envelope slope from 6 to 8 dB/ms, and increasing the peak level improved ITD sensitivity. The combined effect of the off time and slope accounts for the gain in sensitivity for transposed tones relative to SAM tones. In CI listeners, increasing the off time up to 20 ms improved sensitivity, but increasing the slope showed no systematic effect. A 27-pulses/s electric pulse train, representing a special case of modulation with infinitely steep slopes and maximum possible off time, yielded considerably higher sensitivity compared to the best condition with trapezoidal modulation. Overall, the results of this study indicate that envelope-ITD sensitivity could be improved by using CI processing schemes that simultaneously increase the off time and the peak level of the signal envelope.     

Controlling the position of functional groups at the liquid/solid interface: impact of molecular symmetry and chirality

With the aim of controlling the position of functional groups in a substrate-supported monolayer, a new family of functionalized linear alkyl chains was designed and synthesized, aided by molecular mechanics and dynamics simulations of its two-dimensional self-assembly on graphite. The self-assembly of these amino functionalized diamides at the liquid/solid interface was investigated with scanning tunneling microscopy. Intermolecular hydrogen-bonding interactions involving amides, combined with the effect of molecular symmetry and chirality, were found to guide the self-assembly. Control of the relative position and orientation of the amine groups was achieved, in the case of enantiopure compounds. Interestingly, racemates led to both racemic conglomerate and solid solution formation, with a concomitant loss of positional and orientational control of the amino groups as a result.