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We have investigated the hydrolysis of (2) with I equivalent each of water and HCI as a route to labeled aldehydes and ketones. For aldehydes (e.g. pentanal) this method is unsatisfactory because of competing aldol condensation. However, the N-ethyliminium hydrochloride of camphor is a satisfactory precursor of oxygen-labeled camphors.--The N-ethylimine of camphor does not react with benzoyl chloride/Et,N in CHCI, at room temperature over several days. Polymer Model Membranes'"'By Akira Akimoto, Klaus Dorn, Leo Gros, Helmut Ringsdorf, and Hans Schuppl'lThe synthesis of stable model membranes which can be used to study biological processes, for instance cell recognition or cell-cell-interaction, has been a scientific goal for a long time"]. Especially liposomes-artificial, spherical particles with a bimolecular membrane and an aqueous interior-serve as models for biological membranes; however, they show a significantly decreased stabilityI21.synthesized lipids carrying photoreactive groups and could prove a crosslinking of membrane components. Another method to stabilize model membranes providing an even broader scope of possible applications is the polymerization of lipid-analogous (Scheme 1).To stabilize synthetic double layers Khorana et Table 1).All four possibilities in Scheme 1, however, alter the physical properties of the membrane: polymerization in the hydrophobic part of the monomers (examples a-c) especially influences the phase transition temperature, while polymerization in the hydrophilic moiety changes the headgroup properties. Nevertheless, in our opinion, the properties of biological membrane systems can be thoroughly achieved by making the right choice of polymerizable groups. Furthermore, by adding natural phospholipids the properties of biological membranes can be imitated to an even greater extent.The different possibilities shown in Scheme 1 have all been realized. So far only a few contributions have appeared in the literature: acrylate and diacetylene systems have already been described by and by Regen et al. Chapman et al.ISbl, and O'Brien[S'l. Due to the conjugated double bonds of the polymer chain resulting in a rather rigid conformation in poly(diacety1ene) compounds no phase transition temperature can be observed, in contrast to biological memb r a n e~[~~.~~] .New monomer systems for the polymerization according to Scheme 1 are collected in Table 1. The spreading and polymerization behavior of the monomers were investigated at the gas-water interface. The pressure-area diagrams of compounds (3) and (4) qualitatively resemble those of the corresponding diacetylene derivatives[6"1. However, they already show a liquid-analogous phase at substantially lower temperatures. The pressure-area diagram of (5) shows a solid-analogous phase at 2 "C, and a liquid-analogous film with transition to a solid phase at 25 "C (Fig. la).In contrast to the diacetylenes, which react only topothe butadiene and acrylic derivatives can be polymerized by UV light at any temperature in the solidanalogous as ...

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