The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• ) units. The remaining methyl groups are believed to be installed by S-adenosyl methionine (SAM). An intramolecular Aldol condensation generates the pyrrolinone 62, which reacts via an [4 + 2]-cycloaddition to prochaetoglobosin I (63) [56]. Recently, gene disruption studies of Chaetomium globosum revealed

•  12) using a dimethylformamide acetal-mediated cyclodehydration of 105. The isoindole unit of 105 was prepared from the condensation of 103 and 104. Oxygen–sulfur exchange provided the thiophthalimide 105, which could be converted to magallanesine (97) via an intramolecular aldol condensation in one

• lateral metalation–cyclization sequence. Metalation of 130 with excess n-butyllithium followed by carbonation then yielded piperolactam C (131). In 2008, Heo and coworkers reported the synthesis of several aristolactams employing a one-pot cross-coupling/aldol condensation cascade reaction (Scheme 17) [91

Total synthesis of ochnaflavone

• Monica M. Ndoile and
• Fanie R. van Heerden

Beilstein J. Org. Chem. 2013, 9, 1346–1351, doi:10.3762/bjoc.9.152

• formation of the chalcone by an aldol condensation reaction with a suitably substituted acetophenone. Selective methylation of 2,4,6-trihydroxyacetophenone with methyl iodide yielded 2'-hydroxy-4',6'-dimethoxyacetophenone (5) in moderate yield. The Claisen–Schmidt condensation of 5 with diaryl ether 4 under

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• and [11C]-labeled chalcones 19a and 19b were synthesized using similar methods, and a representative synthesis of 19a is shown (Scheme 2B). Aldol condensation between the appropriate acetophenone 22 and benzaldehyde 23 afforded the chalcone backbone, which was subsequently pegylated to give 24 and

Direct alkenylation of indolin-2-ones by 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles: a novel approach

• Sandeep Kumar,
• Ramendra Pratap,
• Abhinav Kumar,
• Brijesh Kumar,
• Vishnu K. Tandon and
• Vishnu Ji Ram

Beilstein J. Org. Chem. 2013, 9, 809–817, doi:10.3762/bjoc.9.92

• only recently been reported. There are plenty of literature reports available on the construction of 3-alkenylindolin-2-ones [21]. The widely used highly facile protocol for the alkenylation of indolin-2-ones is through aldol condensation [22] of isatin with compounds containing an active methylene

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• for constructing highly functionalized and enantiomerically enriched tetrahydro-6H-benzo[c]chromenes with five stereogenic centers. The reaction involved a domino oxa-Michael–Michael–Michael–aldol condensation of o-hydroxy-β-nitrostyrene 15 and two equivalents of α,β-unsaturated aldehydes in the

• ).The protocol involved a tandem oxa-Michael–Michael reaction of 3-methyl-but-2-enal (22) and (E)-2-(2-nitrovinyl)-benzene-1,4-diol (21) followed by a domino Michael–aldol condensation with aldehyde 24 in the presence of TMS-protected diphenylprolinol Ib/AcOH as catalyst, affording the hexahydro-6H

• -nitrostyrene, as reported by Das and co-workers. Enantioselective synthesis of 2-aryl-3-nitro-2H-chromenes, as reported by Schreiner. (S)-diphenylpyrrolinol silyl ether-promoted cascade thio-Michael–aldol reactions, as reported by Wang. Organocatalytic asymmetric domino Michael–aldol condensation of

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• upon intramolecular aldol condensation [25][26][27]. Subsequently, the aldehyde 15 was reduced to the allylic alcohol 19 with LiAlH4 and converted into the acetate 20 [28]. Hydroboration of 20 using disiamylborane proceeded with high stereoselectivity affording 16 as a single stereoisomer [17][28

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

• Hiroki Oguri,
• Haruki Mizoguchi,
• Hideaki Oikawa,
• Aki Ishiyama,
• Masato Iwatsuki,
• Kazuhiko Otoguro and
• Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

• CoA as a starter unit, modular and iterative assembly of malonate extender units produces a linear tetraketide intermediate capable of being folded in at least two ways [5]. Intramolecular Claisen condensation and subsequent enolization produce phloracetophenone (path A), while aldol condensation

Phytoalexins of the Pyrinae: Biphenyls and dibenzofurans

• Cornelia Chizzali and
• Ludger Beerhues

Beilstein J. Org. Chem. 2012, 8, 613–620, doi:10.3762/bjoc.8.68

• intermediate, which undergoes intramolecular C2→C7 aldol condensation and decarboxylative elimination of the terminal carboxyl group to give 3,5-dihydroxybiphenyl (Figure 4). BIS activity was first detected in cell cultures of S. aucuparia treated with yeast extract as an elicitor [22]. A BIS cDNA was cloned

Catalyst-free and solvent-free Michael addition of 1,3-dicarbonyl compounds to nitroalkenes by a grinding method

• Zong-Bo Xie,
• Na Wang,
• Ming-Yu Wu,
• Ting He,
• Zhang-Gao Le and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2012, 8, 534–538, doi:10.3762/bjoc.8.61

• ], Aldol condensation [18], etc. [1][2][19][20]. The Michael addition is one of the most fundamental and important reactions for the formation of carbon–carbon bonds and carbon–heteroatom bonds in organic synthesis. The conjugate Michael addition of carbon nucleophiles to electron deficient nitroalkenes is

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• [14]. This strategy was also successfully applied to the preparation of some furanyl-substituted terpyridines. The synthetic sequence starts from furanyl aldehydes 1–3 and 2-acetylpyridine (4). The first step is a base-mediated aldol-condensation that yields the α,β unsaturated ketones 5–7. Reacting

Aldol elaboration of 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridin-4-ones, masked precursors to acylpyridones

• Raymond C. F. Jones,
• Abdul K. Choudhury,
• James N. Iley,
• Mark E. Light,
• Georgia Loizou and
• Terence A. Pillainayagam

Beilstein J. Org. Chem. 2012, 8, 308–312, doi:10.3762/bjoc.8.33

• MK7 6AA, United Kingdom EPSRC National Crystallography Service, School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom 10.3762/bjoc.8.33 Abstract A core 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridine-4-one scaffold is elaborated at C-3(Me) by base-mediated aldol

• condensation to give new 3-alkenyl-4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridine-4-ones, which are masked forms related to the acylpyridone natural products. Keywords: aldol reaction; fused-ring systems; heterocycles; isoxazole; metalation; pyridone; Introduction The 3-acyl-4-hydroxypyridin-2-one moiety 1

Coupled chemo(enzymatic) reactions in continuous flow

• Ruslan Yuryev,
• Simon Strompen and
• Andreas Liese

Beilstein J. Org. Chem. 2011, 7, 1449–1467, doi:10.3762/bjoc.7.169

• formate decarboxylase (BFD) catalyzing the (S)-selective aldol condensation of benzaldehyde (33) and acetaldehyde (32) with formation of (S)-2-hydroxy-1-phenyl-propanone (34) (Scheme 11). In the second vessel the intermediate (S)-34 was asymmetrically reduced by recLb-alcohol dehydrogenase (ADH) and the

A racemic formal total synthesis of clavukerin A using gold(I)-catalyzed cycloisomerization of 3-methoxy-1,6-enynes as the key strategy

• Jae Youp Cheong and
• Young Ho Rhee

Beilstein J. Org. Chem. 2011, 7, 740–743, doi:10.3762/bjoc.7.84

• in the formal synthesis of clavukerin A was explored. We first investigated the cyclization–hydrogenation strategy (path A in Scheme 4). Deprotection of 4 and the aldol condensation of the resulting diketone under basic conditions proceeded smoothly to give the enone 2 in good yield. However

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• and the final product 4. The isolated intermediate 5 could be transformed into a mixture of 6 and 4 under the reaction conditions, finally yielding 4 via intramolecular aldol condensation. This gold-catalyzed cyclization of alkynyl ketones to enones was successfully utilized in a cascade reaction by

• before being transformed into the final product via intramolecular aldol condensation. Fiksdahl and co-workers investigated a similar gold-catalyzed transformation of internal 1,6-diynes 18 in methanol at room temperature (Scheme 14) [50][51]. Interestingly, a non-conjugated five-membered cyclic enone 19

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• ] (Figure 3). Structurally, this medication consists of a complex pyrrole-substituted 2-indolinone core which can be prepared by a late stage aldol condensation between a 2-indolinone fragment 42 with the corresponding pyrrole aldehyde 41 (Scheme 7). The oxime functionality in compound 38, which is obtained

• ethyl 2,4-dimethylpyrrole-3-carboxylate which can be formylated at the free ring position by trimethyl orthoformate to yield the fully elaborated pyrrole aldehyde (41). The aforementioned aldol condensation unites both key fragments: Ester hydrolysis and amide formation complete the synthesis (Scheme 7

• oxime 38 under reductive conditions. Deprotection and decarboxylation of the remaining tert-butyl ester produces the desired pyrrole intermediate, which upon treatment with Vilsmeier reagent undergoes a formal acylation. This product is not isolated but reacted directly with 41 in an aldol condensation

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• significantly higher when compared to a carousel-type reactor typically used for parallel synthesis. Organocatalytic asymmetric aldol reactions in microflow devices were recently reported by our laboratory [15]. The aldol condensation of various aromatic aldehydes with acetone was carried out at higher

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48