Concise synthesis of two trisaccharide analogs related to the glycone constituent of Phanoside, a novel insulin releasing natural product

Two trisaccharides (2 and 3) related to related to the glycone part of Phanoside, an insulin release stimulator have been synthesized in excellent yield.

A New Synthetic Approach to 8-Aza Analogs of Prostaglandins

A new synthetic approach to (dl)-8-aza-13,14-dihydroprostanoic acid and its corresponding 11-hydroxy derivative is described

Carbamyl Analogs of Phosphatidylcholines Synthesis, Interaction With Phospholipases and Permeability Behavior of their Liposomes

A novel class of phospholipase-resisting phosphatidylcholine analogs, in which the C-2 ester group or both C-1 and C-2 ester groups have been replaced by carbamyloxy functions (-NH-C-O-), have been synthesized. These lipids were not degraded by phospholipase A2 while complete hydrolysis occurred with phospholipase C. Ultrasonic irradiation of the aqueous dispersions of the phospholipids in the presence as well as in the absence of cholesterol resulted in the formation of closed bilayer structures as evidenced by negative staining electron microscopy and also by their ability to entrap [14C]glucose. The leakage rates of glucose at 37°C from liposomes of these compounds have also been measured. Liposomes consisting of 1,2-dipentadecanylcarbamyloxy-sn-glycero- 3-phosphorylcholine were found to be more leaky (2.1 %/h) as compared to the liposomes of 1-palmitoyl-2-pentadecanylcarbamyloxy-sn -glycero-3-phosphoryl- choline (O.5%/h). Moreover, inclusion of cholesterol (33 mol%) into the bilayers of the former phospholipid had no effect on the leakage rate (2.4%/h) while it effectively reduced permeability of the latter (O.22%/h). These phosphatidylcholines are useful for studying the possible role of phospholipases in the capture and lysis of liposomes in vivo.

Effect of Altered Polar Headgroup of Phosphatidylethanolamines on Transbilayer Aminophospholipid Distribution in Sonicated Vesicles

The transbilayer aminophospholipid distributions in small unilamellar vesicles comprising of phosphatidylethanolamine or its analogs (bearing modifications in the polar headgroup) and egg hosphatidylcholine were ascertained using trinitrobenzenesulfonic acid as external membrane probe. These vesicles, containing 10-30 mol% phosphatidylethanolamine or its analogs, were formed by sonication and fractionated by centrifugation. Phosphatidylethanolamine at low concentrations (10 mol%) preferentially localized in the outer monolayer. This preference appeared to be reversed at higher phosphatidylethanolamine concentrations (30 mol%). Unlike this finding, phosphatidylethanolamine bearing ethyl, phenyl and benzyl substituents at the carbon atom adjacent to the amino group distributed mainly in the outer surface irrespective of their concentrations. Similar results were obtained when the phosphate and amino groups were separated by three methylene residues. These observations suggest that the effective polar headgroup volume and/or hydrogen-bonding capacity of phospholipids are the important factors that determine their distribution in small unilamellar vesicles.