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

• subdivided into cytochalasins [41] (phenylalanine), chaetoglobosins [45][46] (tryptophan), aspochalasins [47] (leucine), pyrichalasins [48] (tyrosine) or alachalasins [49][50] (alanine). The biosynthesis of cytochalasans was established on the basis of various isotope labeling experiments using cytochalasin

• relationship between these three classes [87][96]. The biosynthesis of aristolochic acid I (117) was elucidated via labeling experiments and is depicted in Scheme 14 [97][98][99][100]. First, two molecules of the amino acid L-tyrosine (98) are transformed to (R)-orientaline (121) in a similar fashion as

Gold-catalyzed cyclization of allenyl acetal derivatives

• Dhananjayan Vasu,
• Samir Kundlik Pawar and
• Rai-Shung Liu

Beilstein J. Org. Chem. 2013, 9, 1751–1756, doi:10.3762/bjoc.9.202

• deuterium labeling experiments supports a 1,4-hydride shift of the resulting allyl cationic intermediates because a complete deuterium transfer is observed. We tested the reaction on various acetal substrates bearing a propargyl acetate, giving 4-methoxy-5-alkylidenecyclopent-2-en-1-ones 4 via a degradation

• the product without deuterium content (Scheme 2, reaction 2). The results of these labeling experiments reveal a 1,4-hydrogen shift [20][21][22] in the d1-1a→d1-4a transformation. Scheme 3 shows a plausible mechanism to rationalize the transformation of the allenyl acetal 1e into the observed

• % yields. Conclusion In summary, we report a gold-catalyzed transformation of allenyl acetals 1 into 5-alkylidenecyclopent-2-en-1-ones 4. Our deuterium labeling experiments support a 1,4-hydride shift for the resulting allyl cation because of a complete deuterium transfer. This observation excludes the

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• filled by an agostic interaction prior to the C–H bond activation. Intermediate 53 evolves through a σ-CAM process, whereas intermediate 54 undergoes oxidative addition and reductive elimination processes. The release of methane and dimethylsulfide yields 55. Further studies including labeling

• experiments support the reversibility of these “rollover” reactions. The highly unsaturated species 55 is still reactive and can coordinate and decompose XMe2 molecules (X = S [128] and O [129]) and dehydrogenate alkanes [130]. Finally

Chemical–biological characterization of a cruzain inhibitor reveals a second target and a mammalian off-target

• Jonathan W. Choy,
• Clifford Bryant,
• Claudia M. Calvet,
• Patricia S. Doyle,
• Shamila S. Gunatilleke,
• Siegfried S. F. Leung,
• Kenny K. H. Ang,
• Steven Chen,
• Jiri Gut,
• Juan A. Oses-Prieto,
• Jonathan B. Johnston,
• Michelle R. Arkin,
• Alma L. Burlingame,
• Jack Taunton,
• Matthew P. Jacobson,
• James M. McKerrow,
• Larissa M. Podust and
• Adam R. Renslo

Beilstein J. Org. Chem. 2013, 9, 15–25, doi:10.3762/bjoc.9.3

• ., cathepsin B) and/or other cytosolic nucleophiles (e.g., glutathione). This possibility is supported by our competitive labeling experiments (Figure 6) and by in vitro studies employing physiological concentrations of glutathione (Supporting Information File 1). With regard to the inhibitor chemotypes

Identification and isolation of insecticidal oxazoles from Pseudomonas spp.

• Florian Grundmann,
• Veronika Dill,
• Andrea Dowling,
• Aunchalee Thanwisai,
• Edna Bode,
• Narisara Chantratita,
• Richard ffrench-Constant and
• Helge B. Bode

Beilstein J. Org. Chem. 2012, 8, 749–752, doi:10.3762/bjoc.8.85

• A and B. Labeling experiments confirmed their structures and gave initial evidence for a novel biosynthesis pathway of these natural oxazoles. In order to confirm their structure, they were synthesized, which also allowed tests of their bioactivity. Additionally, the bioactivities of the synthesis

• characteristic fragment ion of 130 m/z [M + H]+ (Supporting Information File 1, Figure S2), and labeling experiments (Supporting Information File 1, Figure S3) enabled the elucidation of this ion as 3-methylidene-3H-indolium (Figure 1). In order to determine the genus of the producing strain PB22.5, we sequenced

• produces compounds 3–6 but not 1 and 2. Furthermore two novel oxazole derivatives named labradorin 3 (7, 268.4 m/z [M + H]+, C17H20N2O) and labradorin 4 (8, 283.2 m/z [M + H]+, C18H22N2O) were detected, but they could not be isolated due to their very low production. Labeling experiments were performed in

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• sp3-hybridized C–H bond can be achieved by undergoing 1,3-addition to a vinyl–carbenoid intermediate [142]. The bicyclo[3.2.1]oct-6-en-2-ones 265 and 267 could be synthesized stereoselectively by this method. Deuterium labeling experiments indicated the cyclization involved an unprecedented 1,3

• via oxidative gold catalysis and provided expedient access to various substituted N- or O-heterocycles (344–351) (Scheme 57). Deuterium labeling experiments were carried out to unveil the reaction mechanism. The results established the anti nature of the alkene functionalization and the indispensable

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• selectivity and 90% yield (Scheme 9a) [91]. Labeling experiments showed that the proposed mechanism where the cation is trapped by the nucleophile and subsequent loss of the proton and protodemetallation is viable. A more elaborate study of 5-endo hydroxy- and alkoxycyclizations of 1,5-enynes was described by