The 2-N-acetylamino-2-deoxy class of carbohydrates is ubiquitous among biologically important complex oligosaccharides and glycoconjugates, including, inter alia, glycosaminoglycans, peptidoglycans, and blood group antigens. [1] As a result, the efficient preparation of this group of glycosides
Experimental Section
The synthesis of G1 ยฑ G3 has been recently reported. [8] Langmuir and LB films: Spreading solutions were prepared by dissolving G1 ยฑ G3 in CHCl 3 (1.0 ยฑ 3.0 mg mL ร1 ). Stock solutions proved stable for several months at room temperature. Stock solution (50 mL) was spread on the water surface with a microsyringe, and the film was left for 15 ยฑ 20 min to equilibrate before the compression was started. Data were collected with a KSV LB5000 system (KSV Instruments, Helsinki, Finland) using a symmetrical compression Teflon trough and hydrophilic barriers in a dustfree environment. The whole setup was in a Plexiglas enclosure resting on a vibration-free table, and the trough temperature was controlled to AE 0.1 8C. All isotherms were taken at 20 8C unless otherwise specified. Ultra pure water (1 18.2 MW cm ร1 ) obtained from a Milli-RO3 Plus system combined with a Milli-Q185 Ultra Purification system from Millipore was used for the subphase. Surface pressure was measured by the Wilhelmy plate method. The monolayers were compressed with speeds ranging from 1.2 to 10 2 molecule ร1 min ร1 , with almost no incidence of the barrier velocity on the observed behavior.
LB films were obtained by transfer on glass slides or silicon wafers (100) rendered hydrophobic through silanization of the surface with octadecyltrichlorosilane. The vertical dipping method was used for G1 and G3, while G2 could only be transferred with the horizontal (LS) method. Dipping parameters were not very stringent and usually kept around the following values: trough 30 ยฑ 40 8C, dipping speed % 0.5 ยฑ 4 mm min ร1 . Transfers were performed at surface pressures 12, 15, and 22 mN m ร1 for G1, G2, and G3, respectively. It has been possible to build Y-type multilayer films of G1 and G3.
Grazing incidence X-ray analysis (GIXA): The studies of LB films were performed on a XPERT-MPD device (Philips), equipped with a programmable divergence slit (1/328), a Soller slit collimator, a flat Ge monochromator, and proportional Xe detector. A nickel-filtered Cu Ka line (l 0.1542 nm) was used.
All measurements were recorded immediately after the film transfer, but the diffraction patterns remained stable for as long as several weeks without special care being taken for the storage of the film. BAM: BAM was performed using a BAM2plus (Nanofilm Technologies GmbH) illuminated by an Ar laser. Images were recorded on a CCD camera of field 620 mm ร 500 mm.