Synthesis of phospholipid derivatives as antifungal agents synthetic studies toward the total synthesis of roquefortine C

Abstract

본 논문은 part I와 part II 두 부분으로 구성되어 있다. Part I는 항진균적 생리 활성을 지닌 phospholipid 유도체의 전합성에 관한 내용이고, part II는 mycotoxin의 일종인 Roquefortine C의 전합성에 관한 내용이다. Part I : 녹용으로부터 추출된 lysophosphatidylcholine 화합물들은 항진균적 생리 활성이 나타나나, 기존 시판되고 있는 항진균 치료제에 비해 그 효능이 낮게 나왔다. 본 연구에서는 더 좋은 항진균 치료제를 개발하고자 하여 추출된 화합물의 유도체를 새로이 design, 합성하였다. 출발 물질로는 아미노산인 L-serine과 enatiomer인 D-serine을 선택하여 methyl esterification과 amide bond formation을 시켜주었다. Phosphatidylcholine을 도입하기 위해 ethylene chlorophosphite을 사용하여 phosphoylation을 시켜주었고, P(III) oxidation, ring opening, 그리고 hydrolysis를 시켜준 후, amination을 하여 원하는 phosphatidylcholine moiety를 갖는 (R)-NALPCE과 (S)-NALPCE를 각각 enantioselective 하게 합성, 연구할 수 있었다. 이들은 각각 총 6 단계, 11%와 10%의 수득률로 합성할 수 있었고, 각각의 [α] 값은 -8.4 ˚와 +8.8 ˚으로 얻을 수 있었다. 또한, 각각의 (R)-NALPCE과 (S)-NALPCE으로부터의 reduction을 통해 (R)-NALPC과 (S)-NALPC를 각각 enantioselective 하게 합성, 연구할 수 있었다. 이들은 각각 총 7 단계, 6%의 수득률로 합성 할 수 있었고, 각각의 [α] 값은 +5.3 ˚와 ?5.3 ˚으로 얻어졌다. 결론적으로 sn-1 위치에 methyl ester 또는 hydroxyl group, sn-2 위치에는 N-stearoyl amide, 그리고 sn-3 위치에는 phosphatidylcholine을 가지고 있는 phospholipid를 enantioselective하게 합성에 성공하였다. 이 유도체들은 추출물보다 좋은 항진균적인 생리 활성 가진 것으로 나타났다. Part II : 곰팡이들에 의해 생성되는 mycotoxin은 다양한 독성과 생리 활성을 지니고 있다. 본 연구에서는 이 중에서 Penicillium roqueforti로부터 추출된 Roquefortine C를 전합성 하고자 하여 그 중간 물질을 합성, 연구하였다. 아미노산인 L-tryptophan을 출발물질로 하여 Z-protection, methyl esterification, oxidation을 통해 oxyindole 유도체를 형성시켜 주었다. Z group을 Boc으로 새로이 protection 시켜준 후, thionation과 methylation을 통해 thio-methyl 유도체를 형성시켜 주었다. Reverse prenyl group의 도입은 thio-Claisen rearrangement를 거쳐 diastereomer로 얻을 수 있었다. 이를 가지고 reductive desulfurization을 통한 cyclization을 시도하기 위해 여러 가지 시도를 하였으나, 성공하지 못하였다. 따라서 thio-methyl 유도체에 imidazole을 먼저 coupling 시켜주기 위해 imidazole과 glycine을 aldol condensation을 시키려 하였으나, 이 역시 반응이 진행 되지 않았다. 따라서 L-tryptophan으로부터 reverse prenyl group이 도입된 thio-methyl 유도체까지 전체 7 단계, 28%의 수득률로 얻을 수 있었다. ; Part I : Lysophosphatidylcholine (LPC) compounds from deer antler showed antifungal activities. LPC compounds, isolated phospholipid from deer antler, were demonstrated the hyphal transition suppressing activity, but these were not effective as compared with existing antifungal agents. In this study, we designed and synthesized the derivatives of LPC. Synthesis began with L-serine and its enantiomer D-serine. After formation of methyl ester, primary amine was converted to N-stearoyl amide by amide bond formation with stearic acid. Insertion of the phosphatidylcholine (PC) moiety was performed by the following sequential reactions: P(III) oxidation, ring opening, hydrolysis, and amination. After all, we synthesized (R)-N-acyllysophosphatidylcholine Ester (NALPCE) and (S)-NALPCE in overall 11% and 10% yields in six steps, enantioselectively. (R)-N-acyllysophosphatidylcholine (NALPC) and (S)-NALPC were synthesized by reduction from (R)- NALPCE and (S)-NALPCE overall 6% yields in seven steps, enantioselectively. In conclusion, phospholipid derivatives were designed and synthesized, the methyl ester or the hydroxyl group at the sn-1 position, the N-stearoyl amide at the sn-2 position, and phosphatidylcholine at the sn-3 position, enantioselectively. And these derivatives have the better hyphal transition suppressing activity than isolated compounds. Part II : Many of fungi produce poisonous metabolic products in human food which are dangerous for man. These poisonous substances are called mycotoxins. Mycotoxins display variety of toxic-pharmacological activities. Roquefortine C from Penicillium roqueforti is a kind of mycotoxin. In this study, we carried out synthetic studies toward the total synthesis of Roquefortine C. Synthesis began with natural amino acid, L-tryptophan. Oxyindole derivative was performed by Z-protection, esterification, and oxidation. Z group was converted to Boc group by hydrogenation with Boc anhydride. Thio-methyl indole derivative was synthesized by thionation and methylation with Lawesson s reagent and methyl iodide for good leaving group. Reverse prenyl group was introduced diastereomers by thio-Claisen rearrangement. The 5-Membered cyclization was attempted under various conditions, but it was failed. So, coupling of thio-methyl indole derivative with imidazole ring was attempted by aldol condensation, but it was also unsuccessful. In conclusion, reverse prenylated thio- methyl indole derivative was synthesized from L-tryptophan overall 28% yield in seven steps.