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Une étude bibliographique a été réalisée sur les émissions expiratoires bucco-nasales. Cette étude présente les différents paramètres physiques à prendre en compte ainsi que leurs influences sur l'évolution de ces émissions expiratoires. Les mécanismes de transport et d'atomisation sont décrits à partir de travaux expérimentaux et numériques rapportés dans la littérature. Ces mécanismes font apparaître deux catégories d'objets : de très fines particules appelées aérosols et de plus grosses gouttes dont la taille varie entre quelques dizaines et quelques centaines de microns. Ces objets sont en quantité variable et se propagent différemment selon certains paramètres portant sur le mode d'expiration considéré, le sujet expirant et l'environnement., A bibliographic review on human muco-salivary ejecta is presented. This review presents the various physical parameters that must be accounted for as well as their influence on the evolution of these ejecta. The atomization and transport mechanisms are described from experimental and numerical investigations of the literature. These mechanisms reveal two object categories: very small particles named aerosols, and coarser droplets whose size varies from a few tens and a few hundreds of micrometers. These objects are of various amount and propagate differently according to parameters related to the expiration mode, the volunteer and the environment.

The α and β acetylated (5‐formyl‐2‐furyl)methyl‐D‐glucopyranosides were synthesized and converted into acetylated ranunculin diastereoisomers and δ‐glucosyloxy‐γ‐oxo esters.

The comparative chemical oxidation of isomaltulose and methyl isomaltuloside is described using TEMPO or Pt catalysts.

The comparative chemical oxidation of isomaltulose and methyl isomaltuloside is described using TEMPO or Pt catalysts.

The title tricyclic compound was obtained by photooxygenation of bis(5-formylfurfuryl) ether, followed by a dehydration reaction. The compound appears as a trans isomer, with respect to the relative positions of the lactonic rings to the dioxane ring, which remains chair shaped. Such a trans configuration has been found previously in anemonin, where the two lactonic rings are trans with respect to the cyclobutane ring

Resume Photolysis of (3-oxo butyl)-2,3,4,6-tetra-O-acetyl- β -D-glucopyranoside leads by a stereospecific cyclisation to a C-1-spiro sugar; the conformation of the anomeric carbon is retained.

The spiroketal systems can be obtained easily by a Norrish type II reaction applied to tetrahydropyranic ketoacetals having a carbonyl group in δ position of the acetalic hydrogen. The structures of spirans and bispirans established by IR, NMR ( 1 H and 13 C show an axial conformation for the C-O bond of the tetrahydrofuran ring. With the bispirans this anomeric effect requires for some isomers a twist boat conformation of the tetrahydropyran ring.

The three 3JHH coupling constants observed in the 1H NMR spectra (500 MHz) of trioxa-bis-spirocital 1 and 2 serve to calculate the dihedral angles Ψ(8,9) and Ψ(9,10) of these two molecules. The values obtained, 54° for 1, 25° for 2, reflect the change in conformation: chair → crossed ship when passing from 1 to 2. This change in conformation corresponds in 13C NMR to strong shielding (−3.6 to −5.5 ppm) of the lines of the carbons C8, C9 and C10.

Les[α-tetrahydropyrannyloxy]-2 tetrahydropyrones-3 (3)se photolysent en tetrahydropyrone-3 (6) et δ-valerolactone (7) avec des vitesses differentes selon leurs structures (S*, R*) ou (S*, S*) determinees par rmn et filiation chimique avec les [α-tetrahydropyrannyloxy]-2 tetrahydro-pyrannes (5) (S*, R*) et (S*, S*). The photochemical irradiation of the 2-[sα-tetrahydropyrannyl-oxy]-3-tetrahydropyrones (3) gives the -3-tetrahydropyrone (6)and the α-valerolactone (7). the structures (S*, R*) or (S*, S*) which were determined by mmr and by comparison with the 2-[α-tetrahydropyrannyloxy]-2tetrahydropyrannes (5) (S*, R*) and (S*, S*) influence the rate of the photolysis

INTRODUCTION In the solid state the trioxa-bis-spiroketal 2 (fig. 1) has a twist-boat conformation (tetrahydropyran cycle) and its infrared absorption and nuclear magnetic resonance (1H at 250 MHz, 13C at 15,06 MHz) spectra let forsee the same conformation in solution.1.

The photolysis of tetrahydropyranic ketoacetals gives a mixture of diastereoisomericspiroketals or bis-spiroketals. The kinetic diastereoisomers are preferentially formed at low temperature ; acid isomerisation produces the thermodynamic diastereoisomers.

Das Chlorhydrin (I) liefert mit 2-Hydroxy-tetrahydropyran in Gegenwart von NaH den Hydroxy-ether (IIa), der zu (IIb) acetyliert wird.