title: Synthesis and biochemical studies of analogs of platelet-activating factor bearing a methyl group at C2 of the glycerol backbone.
abstract: Two platelet-activating factor (PAF) analogs containing a methyl group at C2 of the glycerol moiety were synthesized, and some of their biochemical properties were investigated. 1-O-Hexadecyl-2-C,O-dimethyl-rac-glycero-3-phosphocholine (2-methyl-2-methoxy PAF) was prepared in a synthetic scheme beginning with the etherification of 2-methylpropen-1-ol. A reaction sequence involving hydroxylation, tritylation, alkylation, and detritylation afforded 1-O-hexadecyl-2-C,O-dimethyl-rac-glycerol, which was converted into the phosphocholine. A 2-lyso derivative of this PAF analog (2-methyl-lyso PAF) was synthesized from 1-O-hexadecyl-2-C-methyl-3-O-trityl-rac-glycerol. Benzylation followed by detritylation gave 1-O-hexadecyl-2-C-methyl-2-O-benzyl-rac-glycerol, which was converted into the phosphocholine compound. Hydrogenolysis afforded 1-O-hexadecyl-2-C-methyl-rac-glycero-3-phospholine (2-methyl-lyso PAF). The 2-methyl-lyso PAF analog served as a substrate for the acetyl-CoA-dependent acetyltransferase that acetylates 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine. However, 2-methyl-lyso PAF did not have a significant effect on the activities of a CoA-independent transacylase or of the acetylhydrolase that inactivates PAF, and thus does not appear to be a substrate or an inhibitor, respectively, for these enzymes. In addition, this analog exhibited only one-half of the antitumor activity of rac-1-O-alkyl-2-methoxy-rac-glycero-3-phosphocholine in human leukemic (HL-60) cells, and elicited no hypotensive response in rats and no platelet-activating activity.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase; D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism; D000818:Animals; D000959:Antihypertensive Agents / Q000138:chemical synthesis; D000970:Antineoplastic Agents / Q000138:chemical synthesis; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D008745:Methylation; D010741:Phospholipases A / Q000097:blood; D010972:Platelet Activating Factor / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D012701:Serotonin / Q000378:metabolism*
chemical_list: D000959:Antihypertensive Agents; D000970:Antineoplastic Agents; D010972:Platelet Activating Factor; C053411:1-O-hexadecyl-2-C-methyl-3-phosphatidylcholine; C053410:1-O-hexadecyl-2-C,O-dimethylglycero-3-phosphocholine; D012701:Serotonin; D000123:Acetyltransferases; C027628:acetyl-CoA-1-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyltransferase; D010741:Phospholipases A; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase