Synthesis of (S,Z)-3-[(1H-indol-3-yl)methylidene]hexahydropyrrolo[1,2-a]pyrazin-4(1H)-one: an alternative, enaminone based, route to unsaturated cyclodipeptides
作者:Jernej Wagger、Uroš Grošelj、Anton Meden、Jurij Svete、Branko Stanovnik
DOI:10.1016/j.tet.2008.01.045
日期:2008.3
A series of racemic and enantiopure (S,Z)-3-[(1H-indol-3-yl)methylidene]hexahydropyrrolo[1,2-a]pyrazin-4(1H)-one (cyclic Pro–ΔTrp) dipeptide analogues were prepared. Racemic analogues 6a–c were prepared by direct coupling of racemic cyclodipeptide enaminone (R,S)-5 with various indole derivatives. On the other hand, enantiopure analogues were prepared through a copper(I) catalyzed vinyl amidation reaction
一系列外消旋和对映体纯的(S,Z)-3-[(1 H-吲哚-3-基)亚甲基]六氢吡咯并[1,2- a ]吡嗪-4(1 H)-一个(环Pro–ΔTrp)制备了二肽类似物。外消旋类似物6a – c是通过将外消旋环二肽烯胺酮(R,S)-5与各种吲哚衍生物直接偶联制备的。另一方面,通过铜(I)催化的乙烯基酰胺化反应制备了对映纯类似物,其中无环(S)-Pro-ΔTrp二肽类似物20和21形成了。无环二肽被环化为对映体(S)-Pro-ΔTrp二肽类似物24和25。对于偶联反应,分几个步骤制备乙烯基溴。由乙酸乙酯(7)制备烯胺酮8,并与2-甲基吲哚和2-苯基吲哚偶联,得到9和10。3-(吲哚-3-基)丙烯酸酯9和10在位置2上的直接溴化反应生成乙烯基溴化物11和12。乙烯基溴化物11和12中吲哚氮1'上的Boc保护基在进行铜(I)与N- Boc脯氨酰胺18的偶合之前,先引入苯乙二胺。手性中间体和终产物的对映体纯度主要通过HPLC或1