Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• converted with Boc anhydride to yield Boc-protected amino alcohol 7 in 79% yield (Scheme 2). After removal of the silyl group, a selective oxidation of the primary alcohol in presence of the unprotected 3-hydroxy group unfortunately could not be achieved (reactions not displayed). It was therefore decided

End-group-functionalized poly(N,N-diethylacrylamide) via free-radical chain transfer polymerization: Influence of sulfur oxidation and cyclodextrin on self-organization and cloud points in water

• Sebastian Reinelt,
• Daniel Steinke and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 680–691, doi:10.3762/bjoc.10.61

• the signals of the backbone between 2.0–3.9 ppm and 0.7–2.0 ppm, respectively (see Figure 2 for polymer 9b and Supporting Information File 1, Figure S6 for 8b). Oxidation of the end-group-functionalized polymers. The selective oxidation of the thioether groups to the corresponding sulfoxides was

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• Iguchi and co-workers [44] applied the DVCPR to the total synthesis of the marine prostanoid clavubicyclone [45]. Known aldehyde 33 (see Scheme 7) [46] was subjected to Wittig conditions to furnish an intermediate lactone, which was then opened reductively followed by selective oxidation of the allylic

A protecting group-free synthesis of the Colorado potato beetle pheromone

• Zhongtao Wu,
• Manuel Jäger,
• Jeffrey Buter and
• Adriaan J. Minnaard

Beilstein J. Org. Chem. 2013, 9, 2374–2377, doi:10.3762/bjoc.9.273

• , oxidation and stereoselective methylation using organometallic reagents are the key steps, affording (S)-1 in high enantiomeric purity and in gram quantities. In all these approaches, however, protection of the primary hydroxy group of the 1,2,3-triol substructure is required for the selective oxidation of

• conclude that the currently obtained 86% ee suffices. (S)-1,3-dihydroxy-3,7-dimethyl-6-octen-2-one (1). Selective oxidation of glycerol [15] and methyl α-D-glucopyranoside. Approach of synthesis of (S)-1. Synthesis of (S)-1 from geraniol. Reagents and conditions: a) D-(−)-diisopropyl tartrate, Ti(OiPr)4

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• is a suitable method to predict at least relative BDH-values of C–H bonds of the spiro compounds at hand. In absolute terms, B3LYP underestimates the BDH systematically by 2.9–4.6 kcal/mol. The experimental observation as summarized in Scheme 3, e.g., the selective oxidation in 2-position of an allyl

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• the O2-mediated selective oxidation of organic compounds and looking for environmentally safe alternatives to metal catalysis. Keywords: autoxidation; free-radicals; metal-free; molecular oxygen; N-hydroxyphthalimide; Introduction The development of efficient and cheap catalytic systems for the

• selective oxidation of organic substrates under mild and environmentally benign conditions represents one of the major challenges in organic synthesis [1]. In this context, the replacement of traditional oxidants, often used in stoichiometric amounts, with molecular oxygen is mandatory in order to improve

• the beneficial impact of selective oxidation on industrial chemistry [2][3][4][5]. Nevertheless, classical autoxidation is usually very slow at low temperatures, and catalysis is required to activate O2. Transition-metal salts are particularly effective for this scope [6], but their use is often

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

• Matthew T. Richers,
• Chenfei Zhao and
• Daniel Seidel

Beilstein J. Org. Chem. 2013, 9, 1194–1201, doi:10.3762/bjoc.9.135

• to affect the selective oxidation of ring-fused aminals to dihydroquinazolines and quinazolinones, respectively. These methods enable the facile preparation of a number of quinazoline alkaloid natural products and their analogues. Keywords: aminal; copper; oxygen; tert-butylhydroperoxide

NHC-catalysed highly selective aerobic oxidation of nonactivated aldehydes

• Lennart Möhlmann,
• Stefan Ludwig and
• Siegfried Blechert

Beilstein J. Org. Chem. 2013, 9, 602–607, doi:10.3762/bjoc.9.65

• Lennart Mohlmann Stefan Ludwig Siegfried Blechert TU-Berlin – Berlin Institute of Technology, Institute of Chemistry, Straße des 17. Juni 115, 10623 Berlin, Germany. Fax: (+49)-30-314-29745; Tel:(+49)-30-314-22255 10.3762/bjoc.9.65 Abstract This publication describes a highly selective oxidation

• -free oxidation; N-heterocyclic carbene; organocatalysis; Introduction The development of efficient and selective aerobic oxidation methods for organic substrates is of increasing interest and an attractive goal in green chemistry [1][2][3]. In a recent communication we reported on selective oxidation

• mild method for more interesting chemoselective transformations. Therefore, several substrates were oxidised under our conditions bearing either a second alcohol or aldehyde functionality. Desymmetrization of dialdehydes by selective oxidation is an important challenge, since symmetric dialdehydes are

A general and facile one-pot process of isothiocyanates from amines under aqueous conditions

• Nan Sun,
• Bin Li,
• Jianping Shao,
• Weimin Mo,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2012, 8, 61–70, doi:10.3762/bjoc.8.6

• Nan Sun Bin Li Jianping Shao Weimin Mo Baoxiang Hu Zhenlu Shen Xinquan Hu College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, China State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese

Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

• Aurélie Dos Santos,
• Laurent El Kaim,
• Laurence Grimaud and
• Caroline Ronsseray

Beilstein J. Org. Chem. 2011, 7, 1310–1314, doi:10.3762/bjoc.7.153

• uptake of oxygen helps to control the selective oxidation process. Reactions performed under air were faster but led to intractable mixtures. Analogous hydrazones prepared from pyruvic acid and benzoylformic acid with hydrazine derivatives were tested in this Ugi/oxidative cyclization sequence under

Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

• Abhishek Santra and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2011, 7, 1182–1188, doi:10.3762/bjoc.7.137

• achieved in excellent yield using a [2 + 2] block glycosylation strategy. TEMPO-mediated selective oxidation of the primary alcohol of the tetrasaccharide derivative 8 to the carboxylic group followed by deprotection of the functional groups furnished target tetrasaccharide 1 as its 4-methoxyphenyl

• conversion of O-acetyl group to O-benzyl group [22], (iv) activation of glycosyl trichloroacetimidate and thioglycoside donors by perchloric acid supported on silica (HClO4–SiO2) [23][24][25][26], and late stage TEMPO mediated selective oxidation [27][28][29] of the primary hydroxy group to the carboxylic

• subjected to a reaction sequence involving (a) deacetylation using 0.1 M sodium methoxide in methanol; (b) TEMPO mediated selective oxidation [27][28][29] of the primary hydroxy group leaving secondary hydroxy groups unaffected in a phase transfer reaction condition and (c) removal of benzyl groups for

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• for the second catalytic step mentioned above, a two-fold excess of olefin was used in a way that only half of the olefin could be transformed by EYCM. The utilization of a symmetrical fatty acid diester arising from self metathesis or selective oxidation of oleate leads to improved experimental

Green oxidations: Titanium dioxide induced tandem oxidation coupling reactions

• Vineet Jeena and
• Ross S. Robinson

Beilstein J. Org. Chem. 2009, 5, No. 24, doi:10.3762/bjoc.5.24

• TEMPO for the selective oxidation of alcohols to aldehydes and ketones. In our studies we have been examining similar systems with a view to incorporating them into tandem type processes. Conclusion In summary, we have reported the use of titanium dioxide as a tandem oxidation catalyst, demonstrated by

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

• efficient construction of the adjacent bis-THF backbone (Scheme 22). 1,5,9-Cyclododecatriene (86) was converted to the bis-allylic alcohol 154 through selective oxidation and Wittig extension followed by DIBAL-H reduction. The stereogenic centres in the bis-THF backbone 156 were then installed by sequential

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• , formation of an enol triflate using phenyl triflimide and installation of the isopropyl group by an addition-elimination sequence using a thienylcuprate reagent. Removal of the MOM groups and selective oxidation of the allylic alcohol by MnO2 led to the cycloaddition substrate 33, heating of which at 40 °C