The Synthesis and Isotopic Labelling of Plant Lignans K. Haajanena* N.P. Bottinga and H. Adlercreutzb, aSchool of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, *email [email protected] bDivision of Clinical Chemistry, University of Helsinki, Biomedicum, P.O. Box 63, 00014, Helsinki, Finland. Lignans are found in several foods, mostly in wholemeal rye, seeds, beans and berries. Sesame seed lignans are perhaps best known for their positive health effects as antioxidants. Rye lignans are metabolised to enterolactone, which potentially can protect against coronary heart disease and hormone-dependent cancers.1 The metabolic studies of rye lignans include the quantification of lignans in human plasma2, which needs synthetic standards and isotopically labelled internal standards. Titanium(III) induced radical cyclisation reactions3 were used in the syntheses of most of the furofuran lignans shown below. As a result of the radical mechanism, the lignan molecule is produced in its naturally occurring, lowest energy stereoisomer. The 13C labelled lignans were synthesised using the same strategy, using labelled cinnamyl alcohols prepared with aromatic halides and commercially available K13CN 13 and ethyl [ C2]bromoacetate. A simple enantioselective synthetic route to episesamin is also described. OMe OH O Sesame seed O Rye furofurans O furofurans O R 2 H H MeO H H O O O O HO 1 Pinoresinol R1 = R2 =H 2 Medioresinol R1 = OMe, R2 = H 4 Sesamin, Ar = syn to the adjacent H R 1 3 Syringaresinol R1 = R2 = OMe 5 Episesamin, Ar and H anti O O Oxygenated furofurans Labelled analogues R 3 H H O O 13 Ar2 C 4 [13 R 13 1' C3]Pinoresinol O H C H 13 O 2' [ C3]Medioresinol 13 13 C 3' [ C3]Syringaresinol Ar1 13 3 4 O 4' [ C3]Sesamin 6 Sesamolin R , R = OCH2O, Ar and H syn 7 Episesamolinol R3 = OMe, R4 = OH, Ar and H anti References: 1. S. Heinonen, T. Nurmi, K. Liukkonen, K. Poutanen, K. Wähälä, T. Deyama, S. Nishibe and H. Adlercreutz, J. Ag. Food Chem., 2001, 49, 3178-3186. 2. J. L. Peñalvo, T. Nurmi, K. Haajanen, N. Al-Maharik, N. Botting and H. Adlercreutz, Analytical Biochemistry, 332, 2, 2004, 384-393 3. S. C. Roy, K. K. Rana and C. Guin, J. Org. Chem., 2002, 67, 3242-3248. .