Dialkyl ethers and alkyl fluoroalkyl ethers are obtained in excellent yields by the reaction of alcohols and carbonyl compounds in the presence of Pd/C under the atmospheric pressure of hydrogen, when water produced by the reaction is continuously removed by bubbling hydrogen through the reaction mixture.
A convenient and economical procedure for synthesis of long‐chain 1‐O‐alkyl glyceryl ethers (V) is described. Alkyl glycidyl ethers (II) which were derived from the reaction of alcohols (I) with epichlorohydrin using a phase transfer catalyst were first converted into the corresponding dioxolanes (III) or 1‐O‐alkyl‐2,3‐di‐O‐acetylglycerols (IV). Subsequent hydrolysis of the resultant products provided 1‐O‐alkyl glyceryl ethers (V) in high yields.
In order to clarify the roles of lipids in the water-holding property of stratum corneum, the forearm skin of healthy male volunteers was treated with acetone/ether (1/1) or sodium dodecyl sulfate (5%) for 1-30 min.A prolonged treatment period of 5-30 min produced a chapped and scaly appearance of the stratum corneum without any inflammatory reactions.Under these conditions, there was a marked decrease in the water-holding capacity of the stratum corneum accompanied by a selective loss of stratum corneum lipids such as cholesterol, cholesterol esters, and sphingolipids. Two daily applications of the isolated stratum corneum lipids to experimentally induced dry skins caused a significant increase of conductance r accompanied by a marked improvement in the level of scaling.Meanwhile, the isolated sebaceous lipids exhibited no significant recovery in both the conductance value and the scaling.Out of chromatographically separated fractions of the stratum corneum lipids, topical applications of ceramide fraction induced the highest increase in the conductance value.Topical applications of synthesized pseudo-ceramides also showed a significant recovery of the water-retaining properties accompanied by an improvement in the scaling only when the polar group has an amide bond in the major linkage.Analysis of the alkyl chain structures has revealed that a structural requirement for the recovery of the water retaining capacity is the presence of saturated-straight alkyl chains, not unsaturated or branched alkyl chains. These structural characteristics required for water-retaining function also paralleled their capacity to form multiconcentric lamellae vesicles in vitro which is also capable of acquiring bound water as shown by """"DSe-t'Fiermograms. The present study suggests that ceramides with relatively shorter alkyl chain length serve as a water modulator in the multi-lipid bilayers through the stratum corneum.
Aldohexose, such as D-glucose, D-galactose or D-mannose, reacted with acetone to give the following O-isopropylidene derivatives: 1,2;5,6-di-O-isopropylidene-D-glucofuranose (IA), 1,2;3,4-di-O-isopropylidene-D-galactopyranose (IB) or 2,3;5,6-di-O-isopropylidene-D-mannofuranose dC). The O-isopropylidene derivative (IA-IC) reacted with alkyl/alkenyl halogenide to yield aldohexose ether compounds containing di-in good yields. The Williamson ether synthesis was carried out using phase-transfer catalysis (PTC). The derived aldohexose alkyl ether containing di-O-isopropylidene group was hydrolyzed to give 3-O-alkyl-1,2-O-isopropylidene-D-glucofuranose (V) as a partial hydrolysis product; the complete hydrolysis of I-IV gave, as expected, 3-O-alkyl-glucopyranose (VI), 6-O-alkyl-galactopyranose (VII) or 1-O-alkyl-mannofuranoside (VIII). Further alkylation of (V) with Mel under PTC and subsequent acid hydrOlysis gave 3-0alkyl-5,6-di-O-methyI-D-glucofuranose (X). Methanolysis of I11 with catalytic amounts of H2SO 4 gave 1-O-methyl-6-O-alkyl-D-galactofuranoside (Xl). The elucidation of the galactofuranoside skeleton of (Xl) was determined by means of its 13C nuclear magnetic resonance spectra. The O-alkyl aldohexoses, e.g., X and XI, were evaluated and found to be emulsifiers. JAOCS 72, 73-81 (1995).All melting points are uncorrected. Infrared (IR) spectra were obtained with a Hitachi (Tokyo, Japan) 260-50 IR spectrometer. Both 1H and 13C nuclear magnetic resonance (NMR) spectra were recorded in CDC13 using a Varian (Pale Alto, CA) EM 360L NMR spectrometer. Chemical shifts were measured in ppm downfield from internal tetramethylsilane
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