α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• -hydroxylation of aldehydes [14][15]. Recently, we have reported that organocatalytic photooxygenation of aldehydes affords the desired diols (after in situ reduction) in decent yield with either (R)- or (S)-selectivity depending on a catalysts used [14]. In the presence of prolinamides the (R)-enantiomer

A golden opportunity: benzofuranone modifications of aurones and their influence on optical properties, toxicity, and potential as dyes

• Joza Schmitt and
• Scott T. Handy

Beilstein J. Org. Chem. 2019, 15, 1781–1785, doi:10.3762/bjoc.15.171

• important than the exact substituent (at least for the examples studied), with halogen or hydroxy at the 4-position are red-shifted by roughly 10 nm compared to the unsubstituted compound and any halogen or methyl at the 5-position likewise displays a similar shift. Only hydroxylation at the 6-position

• displays a significant blue shift by roughly 40 nm. With respect to toxicity, halogens were the least toxic substituents, displaying the lowest cytotoxicity when at the 6- or 7-positions. Hydroxylation or substitution at the 4-position invariably lead to higher cytotoxicity, though often times no worse

Fluorine-containing substituents: metabolism of the α,α-difluoroethyl thioether motif

• Andrea Rodil,
• Alexandra M. Z. Slawin,
• Nawaf Al-Maharik,
• Ren Tomita and
• David O’Hagan

Beilstein J. Org. Chem. 2019, 15, 1441–1447, doi:10.3762/bjoc.15.144

• mass spectrometry. Naphthalene 5 was fully converted. Again, initial sulfoxidation dominates, but the second oxidation of the sulfoxide to a sulfone appears to be a slower process, and is outcompeted by aryl hydroxylation reactions. The experiment was conducted three times under similar conditions, all

• significantly more rapid than the second oxidation to the sulfone. The first oxidation gave enantiomerically enriched sulfoxides (Ar–S(O)CF2CH3) in the 54–60% ee range. This could arise by the action of more than one P450 enzyme. There was no evidence of defluorination, or hydroxylation at the terminal -CH3

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• hydroxylation temperature, then a reduced yield of 19b was observed (53%). Indirect hydroxylation of the propylated tartrate enolate was also attempted using CBr4 (at −78 °C) as a more readily available/convenient electrophile, which also gave the hydroxy acetonide 19b presumably by way of hydrolysis on work-up

Easy, efficient and versatile one-pot synthesis of Janus-type-substituted fullerenols

• Marius Kunkel and
• Sebastian Polarz

Beilstein J. Org. Chem. 2019, 15, 901–905, doi:10.3762/bjoc.15.87

• fullerenes with solubility in water. Thus, one important class of fullerene derivatives are the hydroxylated and polyhydroxylated compounds, so called fullerenols (C60(OH)n) [14]. The degree of hydroxylation and with that the solubility of these compounds can be tuned by using different synthetic approaches

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• catalytic NHPI and iodic acid mediated the hydroxylation or amidation of tertiary C–H bonds using either wet nitromethane or dry acetonitrile, respectively [54][55]. The substrate scope of the developed benzylic C–H monooxygenation reaction was examined via the oxidation of substrates containing benzylic C

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• electrophilic hydroxylation at C4 When the lithium enolate of dimethyl N-Cbz-L-glutamate 63 was treated with Davis oxaziridine, an inseparable 9:1 mixture of diastereoisomers was formed with (2S,4S)-64 predominating (Scheme 16) [74]. For sodium and potassium enolates diastereoselectivity of the hydroxylation

• [86][87][88] or a Diels–Alder reaction using acylnitroso compounds [89]. However, when compared with these multistep approaches hydroxylation of pyroglutamic acid derivatives seems to be the simplest option. Treatment of the lithium enolate of benzyl N-Boc-pyroglutamate (S)-86 with Davis oxaziridine

• produced (2S,4R)-87 (Scheme 22) [90][91][92]. HPLC investigation of the reaction mixture showed that (2S,4S)-87 was not formed [90]. Stereospecific hydroxylation occurred on the opposite side to the benzyloxycarbonyl group, i.e., only re-face of the enolate was attacked for steric reasons. It is worth

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• the synthesis of (2-hydroxyaryl)pyridines from 2-arylpyridines via a direct C–H hydroxylation on the aryl ring using several expensive transition metal salts (e.g., Pd(II) [60][61][62][63], Rh(III) [64][65], Ru(II) [66]) as catalysts (Scheme 1a). However, the above methods have several drawbacks such

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

• , PQS is produced through hydroxylation of position 3 by the NADH-dependent flavin mono-oxygenase PqsH [32]. This biosynthetic cascade is also responsible for the generation of the pqs-related metabolites DHQ, 2-AA, and HQNO as well as other AQs having different lengths of the alkyl chain [29][30

The enzymes of microbial nicotine metabolism

• Paul F. Fitzpatrick

Beilstein J. Org. Chem. 2018, 14, 2295–2307, doi:10.3762/bjoc.14.204

• deal of interest in identifying bacteria capable of degrading it. A number of microbial pathways have been identified for nicotine degradation. The first and best-understood is the pyridine pathway, best characterized for Arthrobacter nicotinovorans, in which the first reaction is hydroxylation of the

• . JS614; in this case the genes are chromosomal [6]. As shown in Scheme 1, the pathway begins with hydroxylation of the pyridyl ring of nicotine by the enzyme nicotine dehydrogenase to yield 6-hydroxynicotine [7]. Based on the gene sequence, this enzyme was identified as a member of the family of

• the enzyme. While the dominant form of nicotine found in tobacco is (S)-nicotine, the (R)-stereoisomer is also found at detectable levels [22]. Nicotine dehydrogenase is reported not to be stereospecific, in that it can catalyze the hydroxylation of (R)-nicotine to (R)-6-hydroxynicotine; thus, this

Cobalt-catalyzed peri-selective alkoxylation of 1-naphthylamine derivatives

• Jiao-Na Han,
• Cong Du,
• Xinju Zhu,
• Zheng-Long Wang,
• Yue Zhu,
• Zhao-Yang Chu,
• Jun-Long Niu and
• Mao-Ping Song

Beilstein J. Org. Chem. 2018, 14, 2090–2097, doi:10.3762/bjoc.14.183

• –C or C–heteroatom bonds has attracted more attention [8][9][10][11][12][13]. In particular, the formation of C–O bonds is widely used in the syntheses of pharmaceuticals and functional materials [14][15][16][17]. The direct hydroxylation [18][19] and acetoxylation [20][21][22] have been developed

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• used by Quideau et al. for the α-hydroxylation of phenolic derivatives via oxygenative dearomatization. Quideau et al. showed that iodobiarene 38 was oxidized in situ by m-CPBA to generate the I(III) reagent which is responsible for the hydroxylative naphthol dearomatization affording the product in

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Hypervalent iodine(III)-mediated decarboxylative acetoxylation at tertiary and benzylic carbon centers

• Kensuke Kiyokawa,
• Daichi Okumatsu and
• Satoshi Minakata

Beilstein J. Org. Chem. 2018, 14, 1046–1050, doi:10.3762/bjoc.14.92

• amounts of heavy metal oxidants under high-temperature conditions [14][15]. Because these oxidants are typically highly toxic, their use has remained limited in organic synthesis. Barton et al. reported on the development of a practical method for the decarboxylative hydroxylation using thiohydroxamate

Anodic oxidation of bisamides from diaminoalkanes by constant current electrolysis

• Tatiana Golub and
• James Y. Becker

Beilstein J. Org. Chem. 2018, 14, 861–868, doi:10.3762/bjoc.14.72

• : anodic oxidation; bisamides; constant current electrolysis; methoxylation; Introduction It is well known that the anodic oxidation of amides involving a hydrogen atom at the α-position to the N atom could undergo alkoxylation, carboxylation and hydroxylation at this position [1][2][3][4][5] (Scheme 1

Latest development in the synthesis of ursodeoxycholic acid (UDCA): a critical review

• Fabio Tonin and
• Isabel W. C. E. Arends

Beilstein J. Org. Chem. 2018, 14, 470–483, doi:10.3762/bjoc.14.33

• reduction) and the specific hydroxylation and dehydroxylation of suitable positions in the steroid rings. In this minireview, we critically analyze the state of the art of the production of UDCA by several chemical, chemoenzymatic and enzymatic routes reported, highlighting the bottlenecks of each

• ] reported that a fungal strain (Fusarium equiseti M41) was able to introduce a 7β-hydroxy group into LCA by hydroxylation forming UDCA directly. Later, many other microorganisms with a 7β-hydroxylating activity were discovered in strains of actinobacteria and filamentous fungi [96][97]. The key-enzyme in

• that pathway is a P450-like enzyme that catalyses the specific and irreversible 7β-hydroxylation. On this topic, a recent work by Kollerov et al. [98] describes several DCA modifying filamentous fungi strains (mostly ascomycetes and zygomycetes): the highest 7β-hydroxylase activity level was found in

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• ]. The reaction is catalyzed by [fac-Ir(ppy)3] under visible-light irradiation and proceeds via an oxidative quenching cycle, generating reactive sulfonyl radicals from sulfonyl chlorides. The key to β-hydroxylation is the use of a mixture of acetonitrile and water (5:1) as solvent. They confirmed by 18O

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• most important field of application of this catalytic principle. Based on several highly spectacular recent reports, we thus wish to discuss some of the most important achievements in this field within the context of this review. Keywords: amination; chlorination; fluorination; hydroxylation

• ]. Besides those methods that make use of already α-functionalized carbonyl compounds, the direct stereoselective α-oxygenation or α-hydroxylation of simple prochiral nucleophiles with either oxygen as such, or an electrophilic oxygen species became by far the most important and most thoroughly investigated

• -transfer catalysis [110]. In this seminal investigation, they succeeded in carrying out the direct α-hydroxylation of simple ketones 15 by using O2 in combination with triethylphosphite, which leads to the in situ formation of a reactive hydroperoxide derivative. When using the easily accessible cinchona

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• catalytic amount of potassium iodide (0.2 mmol) and 0.25 mL of tert-butylhydroperoxide (TBHP, 70 wt %) in water (4 equiv) to afford the dihydroisoquinazoline 34a, which got oxidized to the quinazolium intermediate 34b. Hydroxylation of 34b afforded 34c, which was further reacted with nitroalkanes at 50 °C

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• diversity of terpene products is obtained by precise modulation of cyclization and rearrangement steps performed by terpene cyclase enzymes [31], initial functional groups are introduced by hydroxylation of the carbon backbone with highly specific P450 monooxygenases [42][43][44]. At present, terpene

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• other hand, the C–H hydroxylation, either with heteroatom-containing directing groups or without directing groups, has provided various methods for the synthesis of phenols. Compared with traditional methods, the transition-metal-catalyzed phenol synthesis has several advantages: broad substrate scope

• for the synthesis of phenols. In the beginning, palladium catalysts have attracted much attention due to their high conversion efficiency, and later copper catalysts, which are cheaper and more stable, have been extensively studied in this field. 1.1.1 Palladium-catalyzed hydroxylation of aryl halides

• as the base and succeeded in the hydroxylation of aryl halides [22]. They chose tri-tert-butylphosphine as the ligand in their reaction system and obtained the phenols from aryl halides, suggesting a great influence of the ligand on the reaction performance (Scheme 2). However, their protocol was

Biosynthetic origin of butyrolactol A, an antifungal polyketide produced by a marine-derived Streptomyces

• Enjuro Harunari,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2017, 13, 441–450, doi:10.3762/bjoc.13.47

• alternative alignment of the methylene and the oxygenated carbons. Meanwhile, a 1,2-diol in polyketides is known to be formed by hydroxylation of methylene carbons as seen in the biosynthesis of erythromycin or amphotericin B [17][18]. The contiguously hydroxylated carbon chain of 1 is quite unusual as a

• to C-4) and the pentaol (C-5 to C-9) moieties (Figure 3), suggesting that the contiguous polyol system is not formed by methylene hydroxylation. Another possible pathway for 1,2-diol formation is the incorporation of hydroxymalonyl-ACP from a glycolytic intermediate for chain elongation [23]. To

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

• Felicia D’Andrea,
• Giorgio Catelani,
• Lorenzo Guazzelli and
• Venerando Pistarà

Beilstein J. Org. Chem. 2016, 12, 2343–2350, doi:10.3762/bjoc.12.227

• [8][9][10][11][12][13]; 2) elaboration of the six carbon atom skeleton of either a) tetrahydroxycyclohexene derivatives [14][15] (synthetic or natural conduritols) through stereoselective cis-hydroxylation or epoxidation–hydrolysis of the double bond or b) benzene [16][17] or halo-benzenes [18][19