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

• ,3S) to the anti’-6 isomer. Based on the known relationship between syn-6 and anti’-6 diols and the other two diastereoisomers we assigned their absolute configuration as (2S,3S) for syn’-6 and (2S,3R) for anti-6, respectively. Asymmetric synthesis of 3,4-diphenylbutane-1,2-diol To confirm our

• ). Stereoselective α-photooxygenation of 3,4-diphenylbutanal (1) with 1O2. Schematic representation of the in situ methodology and preferred conformation of diols with Mo2 core. Asymmetric synthesis of 3,4-diphenylbutane-1,2-diol. Stereoselectivity of α-photooxygenation reaction of 3,4-diphenylbutanal (1

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• syntheses of triptolide. In 2014, Li and co-workers further reported a formal asymmetric synthesis of triptolide from tetralone 24 (Figure 2, route B and Scheme 2) [50], featuring a Robinson annulation of Nazarov’s reagent 25 with 5-methoxy-2-tetralone 24 in the presence of enantiomerically pure (R)-α

• -workers reported an asymmetric synthesis of triptolide using readily available ʟ-dehydroabietic acid (26) as starting material (Figure 2, route C and Scheme 3) [67]. In this synthesis, the key step was the construction of the butenolide (D-ring). ʟ-Dehydroabietic acid was converted to C-14

• ), minnelide (6) and LLDT-8 (7). Syntheses of triptolide. Berchtold’s synthesis of triptolide. Li’s formal synthesis of triptolide. van Tamelen’s asymmetric synthesis of triptonide and triptolide. Van Tamelen’s (method II) formal synthesis of triptolide. Sherburn’s formal synthesis of triptolide. van Tamelen’s

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• efficiency of a 2-substituted N-(1-phenylethyl)aziridine framework as chiron bearing a chiral auxiliary. Keywords: alkaloids; amino acids; asymmetric synthesis; ceramides; chiral catalysis; chiral pool; N-(1-phenylethyl)aziridine chiron; sphingoids; Introduction The synthesis of enantiomerically pure

• compounds belongs to the most challenging tasks in organic chemistry for several reasons, just to mention structural studies of natural products or preparation of chiral drugs. They become available by asymmetric synthesis frequently employing chiral synthons (chirons) [1]. Chirons contain functional groups

• of chemical and configurational stability was achieved by introducing N,N-dibenzylserinals 4 [10]. Another important strategy of asymmetric synthesis relies on chiral auxiliaries, i.e., a specially selected homochiral part of a starting material governing the stereoselectivity of subsequent reactions

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• cytotoxicity [9]. However, it is of great importance to obtain all stereoisomers for the study of biological activity. Therefore, the development of methods for the asymmetric synthesis of polyfunctional sulfones is valuable. The most notable of them are Ag- and Cu-catalyzed 1,3-dipolar cycloaddition reactions

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• line. A very recent example of a highly diastereoselective Ugi-type MCR was reported by Rivera, Paixão and co-workers using a steroidal isocyanide [31]. As shown in Scheme 9, the procedure comprised the organocatalytic asymmetric synthesis of the chiral bifunctional substrate 30 bearing an masked

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

Dirhodium(II)-catalyzed [3 + 2] cycloaddition of N-arylaminocyclopropane with alkyne derivatives

• Wentong Liu,
• Yi Kuang,
• Zhifan Wang,
• Jin Zhu and
• Yuanhua Wang

Beilstein J. Org. Chem. 2019, 15, 542–550, doi:10.3762/bjoc.15.48

• method has potential synthetic practicality by providing a convenient way to synthesize trans-cyclic β-amino acid derivatives. Further application of this method with other cycloaddition partners and asymmetric synthesis of the chiral ring with the help of chiral auxiliaries are currently underway

A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12

• Seema V. Kanojia,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2019, 15, 490–496, doi:10.3762/bjoc.15.42

• envisaged that the enantiomers of 4 were ideal substrates for the asymmetric synthesis of different stereoisomers of 2. Several biocatalytic protocols for the preparation of (R) or (S)-4 were reported earlier. The hydrolysis of the corresponding acetate with crude enzyme preparations from pig liver and

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• ) derivatives and dipeptides. In this regard, trimerization and Negishi cross-coupling reactions are used as the key steps starting from readily available 4’-iodoacetophenone and L-serine. These C3-symmetric molecules containing AAA moieties are useful to design new ligands suitable for asymmetric synthesis and

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• crucial for the intramolecular cyclopropanation reaction in a water/ether biphasic medium. The water-soluble catalyst could be reused at least six times with little loss in yield and enantioselectivity. Keywords: asymmetric synthesis; carbene transfer; cyclopropanation; diazoester; intramolecular

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

• pyroglutamic acids, proline and 4-hydroxyproline). Since various hydroxyglutamic acids were identified as components of complex natural products, syntheses of orthogonally protected derivatives of hydroxyglutamic acids are also covered. Keywords: amino acids; asymmetric synthesis; chiral catalysis; chiral

Asymmetric synthesis of a high added value chiral amine using immobilized ω-transaminases

• Antonella Petri,
• Valeria Colonna and
• Oreste Piccolo

Beilstein J. Org. Chem. 2019, 15, 60–66, doi:10.3762/bjoc.15.6

• are easily regenerated in situ without the need for another enzyme. In principle, enantiomerically pure chiral amines can be prepared following two approaches: through kinetic resolution starting from racemic amines or by asymmetric synthesis starting from suitable substrates, e.g., the corresponding

• carbonyl compounds. In a kinetic resolution, a maximum yield of 50% of the product can be obtained. Moreover, high quantities of the co-product might complicate the product separation and the recovery of the chiral amine. Thus, the asymmetric synthesis is generally preferable because a theoretically 100

• by using resolution of racemic mixtures, preparation from chiral precursors or asymmetric synthesis from prochiral compounds [20][21][22]. In contrast, only few examples have been published on the synthesis of this molecule through biotransformations [23][24]. In these procedures TAs are used in

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• use of any halide additive. The unsymmetrical NHC catalysts 164, 173 and 174 were also examined in the asymmetric synthesis of [7]helicene (180). Among them, complex 174 exhibited the highest degree of selectivity, leading to the desired product with an enantiomeric excess of 80% [56]. An extension of

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• glycal scaffolds are versatile building blocks with multiple applications in the field of natural product synthesis [6], the development of new asymmetric synthetic sequences with stereochemical diversity is still of high interest. Different approaches have been reported for the asymmetric synthesis of

Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

• Piotr Pomarański,
• Piotr Roszkowski,
• Jan K. Maurin,
• Armand Budzianowski and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214

• asymmetric synthesis of various substituted arylpyridine derivatives. Unfortunately, separation using chiral HPLC columns were unsuccessful and therefore, the racemic mixtures of these atropisomers were examined by 1H NMR spectroscopy with a chiral solvating agent ((+)-(R)-tert-butyl(phenyl)phosphinothioic

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• –2.55 (m, 1H), 2.41–2.37 (m, 2H), 1.90–1.80 (m, 3H), 1.24 (s, 3H); MS (ES+) m/z: 232.18 [M + H]+. Commercial process for the synthesis of 1. Previous work about asymmetric synthesis of I-13a. Asymmetric synthesis of 1. The second strategy for the asymmetric synthesis of 1. Optimization of asymmetric

One-pot synthesis of epoxides from benzyl alcohols and aldehydes

• Edwin Alfonzo,
• Jesse W. L. Mendoza and
• Aaron B. Beeler

Beilstein J. Org. Chem. 2018, 14, 2308–2312, doi:10.3762/bjoc.14.205

• its original disclosure, particular in the area of asymmetric synthesis [22][23][24]. Other notable advancements include the expansion of its scope by using organic bases and a one-pot oxidation/epoxidation sequence of benzyl alcohols with manganese dioxide and an exogenous sulfonium salt [25][26

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

• Michael R. Imrich,
• Jochen Kraft,
• Cäcilia Maichle-Mössmer and
• Thomas Ziegler

Beilstein J. Org. Chem. 2018, 14, 2082–2089, doi:10.3762/bjoc.14.182

• ][22]. This led us to extend the concept of spiro-fused carbohydrate oxazolines for asymmetric synthesis by developing new types of carbohydrate-based PHOX ligands. Herein, we present ten novel spiro-PHOX ligands containing diphenylphosphino groups, 5, which can be synthesized in four to six steps

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• reduction of aromatic β-keto sulfides provided excellent enantioselectivity, the reduction of the corresponding alkyl β-keto sulfides gave low enantioselectivity. Ruano and co-workers reported the asymmetric synthesis of β-hydroxy sulfides via connectivity of a suitably substituted benzylic carbanion with

• biocatalysis for the asymmetric synthesis of β-hydroxy sulfides still remains unexplored. 3.1.2 Disulfides as nucleophiles. Whilst thiols are excellent nucleophiles and can open epoxides under a variety of conditions as detailed above, they can be awfully odoriferous and unpleasant to work with [58]. As an

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• investigated and significant achievements have been reported making iodine compounds now useful organocatalysts in asymmetric synthesis (reaction 2 in Scheme 1a) [15][16][17][18][19][20][21][22][23][24]. In parallel to these investigations, a third strategy has been envisaged with the development of tandem

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• asymmetric synthesis. In 2013, we described a novel class of calix[4]arene-based chiral primary amine–thiourea catalysts 47a and 47b derived from p-tert-butylcalix[4]arene (Figure 7) [49]. To evaluate the catalytic efficiency, bifunctional catalysts were applied to promote the Michael addition of aldehydes

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• imines published since the beginning of 2015. Keywords: asymmetric synthesis; chiral 3-amino-2-oxindoles; chirality; isatin imines; nucleophilic addition; Introduction Chiral oxindoles represent an important class of products widely present in nature and exhibiting many biological activities. Among

• additions to isatin imines have been developed, including Mannich reactions, aza-Morita–Baylis–Hillman reactions, Friedel–Crafts reactions, aza-Henry reactions, additions of heteronucleophiles, Strecker reactions, among others. The goal of this review is to update the catalytic asymmetric synthesis of

• achieved in the past three years in the field of asymmetric synthesis of 3-substituted 3-amino-2-oxindoles through enantioselective nucleophilic additions to isatin imines, involving both chiral metal and organocatalysts. Indeed, a variety of novel methodologies, including enantioselective Mannich

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

• last 25 years. This review highlights the contribution of different chiral hypervalent iodine reagents in diverse asymmetric conversions. Keywords: alkene functionalization; asymmetric synthesis; hypervalent iodine; organocatalysis; oxidation; Introduction It is more than one century ago since the

• ]. They have utilized this chiral difluoroiodonium salt 13 for the asymmetric synthesis of aminofluorinated compounds 66 from 65 (Scheme 14). In addition to this, they extended this methodology for the regioselective intermolecular aminofluorination of styrenes with a racemic catalyst. The nucleophilic

• towards a sustainable replacement of transition metals. The application of chiral hypervalent iodine reagents is expected to pave the way for new reactions and reagent design in the field of asymmetric synthesis and catalysis. An overview of different chiral iodine reagents or precursors thereof

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

A stereoselective and flexible synthesis to access both enantiomers of N-acetylgalactosamine and peracetylated N-acetylidosamine

• Bettina Riedl and
• Walther Schmid

Beilstein J. Org. Chem. 2018, 14, 856–860, doi:10.3762/bjoc.14.71

• : asymmetric synthesis; carbohydrates; N-acetylgalactosamine; N-acetylidosamine; Introduction N-Acetylgalactosamine (GalNAc, Figure 1) and N-acetylidosamine (IdoNAc) belong to the group of 2-amino-2-deoxysugars, which can be found in a wide range of organisms as building blocks of, e.g., glycosaminoglycans