De Novo Asymmetric Synthesis of d- and l-Swainsonine
摘要:
The enantioselective syntheses of both enantiomers of the indolizidine natural product swainsonine have been achieved in 13 steps from furan. The indolizidine ring system is installed by a one-pot hydrogenolysis of both an azide and an O-Bn group along with an intramolecular reductive amination reaction. The asymmetry of swainsonine was introduced by Noyori reduction of an acylfuran. This route relies upon an Achmatowicz rearrangement, a diastereoselective palladium-catalyzed glycosylation, Luche reduction, and a dihydroxylation reaction.
Le de l'ion de l'ion chlorure du complexe (PPh 3 ) 2 Cl-iridacyclopenta-2,4-diene-2,3,4,5-tetracarboxylate detetramethyle,在CH 3 CN 存在下;AgBF 4 ;PMe 3 donne les complexes cationiques de type (PPh 3 ) 2 (L) (L') iridacyclopenta-2,4-diene-2,3,4,5-tetracarboxyle de tetramethyle,avec L=CO ou NCCH 3 ;L=H 2 O 或NCCH 3 。Ces 复合物 reagissent avec soit le but-3-yn-1-ol, soit le pent-4-yn-2-ol。在 obtient des complexes
Taming furfuryl cations for the synthesis of privileged structures and novel scaffolds
作者:Seema Dhiman、S. S. V. Ramasastry
DOI:10.1039/c3ob40814k
日期:——
Furfuryl cations are generated via a highly efficient bismuth-catalyzed reaction of furfuryl alcohols. This systematic study provides insight on the reactivity profile of furfuryl cations towards nucleophilic substitution reactions. Novel C–C, C–N, C–O and C–S bond forming reactions of furfuryl cations have been developed, thus providing access to a diverse array of building blocks for further manipulations.
1,6,7-trioxa-spiro[4.5]decanes were synthesized using the hydrogen peroxide in UHP (urea–H2O2 complex) as the source of the peroxy bond. Incorporation of H2O2 into the organic molecular framework was facilitated by the potential to form a five- or six memberd cyclic hemiketal. Saturation of the double bond in a substituted γ-keto-butenal, a step required in all the syntheses, was achieved in one case
使用过氧化氢在UHP(尿素-H 2 O 2络合物)中合成了四个1,2,7-三氧杂螺[5.5]十一烷和两个1,6,7-三氧杂螺[4.5]癸烷。过氧键。通过形成五元或六元环状半缩酮的潜力,可以促进将H 2 O 2引入有机分子骨架中。在一种情况下,用NaI /浓盐酸在低温下实现了取代的γ-酮-丁醛中双键的饱和,这是所有合成所需要的步骤,而在室温下未裂解TBS保护基或引起过多的副反应。温度。所有这些过氧化物均显示出与天然过氧苯甲酸和已知类似物相当的体外抗疟活性。
Enantioselective Ketone Hydroacylation Using Noyori’s Transfer Hydrogenation Catalyst
作者:Stephen K. Murphy、Vy M. Dong
DOI:10.1021/ja4021974
日期:2013.4.17
An enantioselectiveketone hydroacylation enables the direct preparation of lactones from keto alcohols. The alcohol is oxidized in situ to an aldehyde, obviating the need to prepare sensitive keto aldehyde substrates. Noyori's asymmetric transferhydrogenationcatalyst was applied to address challenges of reactivity, chemoselectivity, and enantioselectivity.
The [5+2]cycloaddition reaction of 2-substituted-3-oxidopyrylium betaine with dialkyl fumarates was found to proceed with stereoselectivity up to 15.5 : 1. The stereoselectivity became higher as either the 2-substituent of the 3-oxidopyrylium or the alkoxy group of the fumarate became larger. The stereoselectivity could be rationalized by considering these steric effects.
De novo asymmetric syntheses of d-, l- and 8-epi-d-swainsonine
作者:Haibing Guo、George A. O'Doherty
DOI:10.1016/j.tet.2007.10.109
日期:2008.1
A highly enantioselective and stereocontrolled approach to d-, l- and 8-epi-d-swainsonine has been developed from achiral furan and γ-butyrolactone. A one-pot hydrogenolysis of both azide and benzyl ether followed by an intramolecular reductive amination has been employed as key step to establish the indolizidine ring system. The absolute stereochemistry was installed by the Noyori reduction and the