The First Stereoselective Synthesis of Racemic .beta.-Multistriatin: A Pheromone Component of the European Elm Bark Beetle Scolytus multistriatus (Marsh.)
摘要:
The first stereoselective synthesis of racemic beta-multistriatin (4), a component of the pheromone of the European elm bark beetle Scolytus multistriatus (Marsh.), is described. Potassium glycerate (23) is alkylated with 2-bromopentanone (26) in the presence of the phase transfer catalyst TDA-1 to form the acyloin ester 29 in 75% yield. After trimethylsilylation of 29, intramolecular acetalization of the product 30 in the presence of catalytic amounts of trimethylsilyl triflate and perchloric acid affords a mixture of diastereomers of the bicyclic lactone 28 in 65% yield. Reduction of 28 with LiAlH4 gives the cis-disubstituted dioxolane diol 34 in 82% yield. Oxidation of both the primary and secondary hydroxy groups present in 34 by a modified Swern oxidation affords the keto aldehyde 35 in 61% yield. The change of the reagent ratio of oxalyl chloride:DMSO:NEt(3) from 1.1:2.4:5 to 1.2:1.2:3 and a nonaqueous workup procedure are crucial for the success of this oxidation. Intramolecular aldol condensation of 35 catalyzed by triethylammonium chloride affords the aldol 38. Acetylation of 38 and pyrolytic distillation give the bicyclic enone 37. Oxidation of 34, aldol reaction, and formation of the enone 37 can be combined in a one-pot procedure to give an overall yield of 21%. 1,4-Addition of lithium dimethylcuprate to the enone 37 affords ketone 36 with the methyl group exclusively in the axial position. After Wittig methylenation of 36, the olefin 40 is obtained in 76% yield. Catalytic hydrogenation of 40 with PtO2 gives a 92:8 mixture of beta- and delta-multistriatin in 85% yield. Acid-catalyzed epimerization of 4 affords delta-multistriatin (5). Some of the compounds prepared (28, 36, 37, and 40) are of interest as multistriatin analogues. Olefin 40 is also a valuable storage form for the unstable beta-multistriatin (4).
已经研究了乙二醇(EG)和甘油(G)的电氧化:在碱性介质中,在被动式和主动式直接乙二醇燃料电池(DEGFCs)中以及在包含Pd-(Ni)的直接甘油燃料电池(DGFCs)中-Zn)/ C作为阳极电催化剂,即负载在Ni-Zn相上的Pd纳米颗粒。为了进行比较,还研究了包含Pd纳米粒子(Pd / C)的阳极电催化剂。EG和G的氧化主要是在半电池中进行的。获得的结果突出了Pd-(Ni-Zn)/ C在峰值电流密度方面的出色电催化活性,对于EG和2150 A g (Pd)-1而言,峰值电流密度高达3300 A g (Pd)-1。膜电极组件(MEA)是使用Pd-(Ni-Zn)/ C阳极,专有的Fe-Co / C阴极和Tokuyama A-201阴离子交换膜制造的。MEA性能已在装有5 wt%EG和5 wt%G的水溶液的无源或有源电池中进行了评估。鉴于在20至80°C的温度范围内,Pd负载下获得的峰值功率密度从阳极上的低至1