Synthesis of the diacetylenic phospholipids 1,2-(10',12'-heptadecadiynoyl)-sn-glycero-3-phophatidylcholine and 1,2-(4',6'-tricosadiynoyl)-sn-glycero-3-phophatidylcholine

Diacetylenic phosphatidylcholines are synthetic compounds analogous to natural phospholipids. These molecules can be hydrated to form bilayered aggregates known as liposomes in a manner similar to natural phosphatidylcholines. A particular feature of these liposomes is their capability of undergoing polymerization when submitted to ultraviolet (UV) light irradiation. This process allows the construction of polymerized liposomes possessing interesting physical properties making these vesicles appropriate for slow-release drug delivering systems. In this article we describe the total syntheses of diacetylenic phosphatidylcholines 1,2-bis(10',12'-heptadecadiynoyl)- sn-glycero-3-phosphatidylcholine (1a), 1,2-bis(10',12'-tricosadiynoyl)-sn-glycero- 3-phosphatidylcholine (1b) and 1,2-bis( 4',6'-tricosadiynoyl)-sn-glycero- 3-phosphatidylcholine (1c). Phospholipids 1a and 1c, displaying the butadiinyl chromophores closer to the chain terminus, or closer to the polar heads respectively, have not been reported before. Noteworthy was the observation that liofilization of the diacetylenic alcohols and acids intermediates significantly reduced undesired polymerization, allowing to stock these compounds for a short period of time (similar to 24 h).