A synthetic route to cardiolipins

It is now well established that biological membranes are based on a phospholipid bilayer. The phospholipid cardiolipin was found to be exclusively located in the inner membrane of the mitochondrion in eukaryotic cells. \nAlthough 35 years have elapsed since it was isolated in a pure state, its function in the mitochondrion still remains a mystery. This is partly due to the difficulties attending its isolation and the laborious and inefficient nature 6f its chemical syntheses reported to date. \nSince no coherent review on cardiolipin has been published, there is presented here (Chapter 1) an up-to-date (concluded with December 1975 issue of Chem, Abs. ) overview of what is known about and what has been proposed for cardiolipins. Bis-phosphatidic acids are also reviewed since, again, for these molecules nearly nothing is known. These molecules arose as by-products in our chemical synthesis of cardiolipins. This chapter, having its own references, constitutes a complete and independent entity of this thesis. \nIn Chapter 2, the current available methodology for the chemical synthesis of cardiolipins is reviewed. In Chapter 4, our repetition of classical procedures, \ni.e. phosphorylations with silver phosphates or phosphorus oxychloride, which gave poor yields or extremely complicated, intractable reaction products, respectively, is described. \nIn an effort to achieve a quick, efficient method for ­unsaturated cardiolipins, a detailed study on the preparation and chemistry of various components of the cardiolipin molecule was carried out. In Chapter 5, the middle glycerol part is described where various protecting groups for alcoholic function have been tested. Best results were obtained using the ¿-butyldimethylsilyl (TBDMS) group. In Chapter 6, various protecting groups, such as TBDMS, acetoacetate, 0, 0, 0-trichloroethoxycarbonyl and o-nitrobenzoyl were tested aiming at their use in the preparation of polyunsaturated 1,2-diacyl- sn-glycerols. No one was found to be satisfactory. Saturated 1, 2-diacyl-sn- glycerols required for this work were therefore prepared using the classical benzyl group, effecting some modifications' in published procedures. \nUnsuccessful application of two phosphorylating agents, bis-(0, g, 0- trichloroethyl) phosphorochloridate and CAP-anhydrides, CXV, to phospholipid chemistry is outlined in Chapter 7, while the successful application of CEP-O-CEP, CXXVIII, for the chemical synthesis of cardiolipins is presented in Chapter 8. Discovery of an intramolecular catalysis by a P-OH group towards a g-located ether bond greatly simplified the synthetic chemistry of cardiolipins. \nStarting from1, 2-diacyl-sn-glycerols three cardiolipin species were prepared in a yield of 20 - 28% by a four step sequence requiring purification only for two of these steps. These yields are similar or better to those published for the classical silver phosphates (Chapters 2 and 4), but our synthesis is achieved in much shorter time.