Glyceryl unit

Fig. 2.14 (a) Molecular structure of a phospholipid, lecithin (n.b. adopted stereochemistry of glyceryl unit), and (b) phospholipid arrangement in cell membranes. 

Another series of branched (dialkyl) nonionic surfactants has been studied (139) having the general formula C tQjGEgM, where Ca and C denote different alkyl chains, with = 4 for n-butyl (C4) and tert-buiy (C4 Q and n = 10 or 12 G denotes a glyceryl unit and... 

This is illustrated in Scheme VI. The protected glyceryl derivatives are insoluble in aqueous media and appear to be hydrolytically stable. The deprotected species (structure 27) is water-soluble and hydrolyzes in aqueous media at neutral pH at 37°C to give glycerol, phosphate, and ammonia. The free hydroxyl units of the deprotected polymer provide sites for the covalent attachment of drug molecules. Water insolubility can be imparted by the use of appropriate hydro-phobic cosubstituent groups to generate solid, erodible materials. 

PROBLEM 24.16 Show the structure of glyceryl trioleate, a fat molecule whose components are glycerol and three oleic acid units. 

Most poly(organophosphazenes) are stable to water. Only a selected few are not. These include polymers with amino acid ester side groups, and species with imidazolyl, glyceryl, or glucosyl side units. These will be discussed later. 

Resistance to heparin has been observed in patients in coronary care units receiving intravenous glyceryl trinitrate. Although this has been imputed to propylene glycol in glyceryl trinitrate formulations (113), resistance has also been described with propylene glycol-free... 

Two emulsifier systems were used for the preparation of O/W emulsions. The first emulsifier was Synperonic PEE 127, an A-B-A block copolymer of poly(ethylene oxide), PEO (the A chains, were about 100 EO units each) and propylene oxide PPO (the B chain was about 55 PO units), supplied by UNIQEMA. The second emulsifier system was Arlatone V-100 (supplied by UNIQEMA), a nonionic emulsifier system composed of a blend of Steareth-100 (stearyl alcohol with 100 EO units), Steareth-2 (stearyl alcohol with 2 EO units), glyceryl stearate citrate, sucrose, and a mixture of two polysaccharides, namely mannan and xanthan gum (Keltrol F, supplied by Kelco). In some emulsions, xanthan gum was used as a thickener. AH emulsions contained a preservative (Nipaguard BPX). 

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