Submitted to: International Symposium on the Synthesis and Application of Isotopes
Publication Type: Proceedings
Publication Acceptance Date: September 14, 1997
Publication Date: N/A
Technical Abstract: An 8-step synthesis was developed to prepare the methyl cis-9,trans-11- and and the trans-9, trans-11-18:2-17,17,18,18-d4 (96%-d4). 5-Hexyn-1-o1 was reduced D2 gas/ Wilkinson's catalyst to yield 1-hexanol-5,5,6,6-d4. The alcohol was converted to the iodide (phosphorous pentoxide/ phosphoric acid/ potassium iodide) and coupled with 2-propyn-1-o1 (lithium amide in liquid ammonia) to yield 2-nonyn-1-ol-dr. The acetylenic alcohol was reduced with lithium metal in liquid ammonia to yield trans-2-nonen-1-ol- d4, converted to the bromide (via. triphenylphos-phine dibromide) and then converted to the phosphonium salt. The isomer pair was obtained by coupling the phosphonium bromide (8,8, 9,9-d4) and methyl 9-oxononanoate. A similar synthesis was used to prepare the trans-10-,cis-12 and cis-10, cis-12-19:2-15,15,16,16-d4 isomer pair (86%-d4). 2-Pentyn-1-ol was used as starting alcohol and the 7-carbon acetylenic intermediate was reduced to the cis-olefin with H2 gas/ Lindlar catalyst. 10-Oxodecanoate was used in the Witting coupling reaction to yield the 10-trans,12-cis- and the 10-cis, 12-cis-18:2 isomer pair. Isomer pairs (ca. 50/50) were readily separated by reversed-phase HPLC and silver resin chromatography (chemical purity >95%; overall yields ca. 20% for each isomer). The cis-10,cis-12-18:2 was isomerized (p-toluenesulfinic acid) to yield the trans-10,trans-12-18:2-d4 isomer in 75% yield.