Derivatives of benzo-1,4-thiazine-3-carboxylic acid and the corresponding amino acid conjugates

• Péter Kisszékelyi,
• Tibor Peňaška,
• Klára Stankovianska,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 1195–1202, doi:10.3762/bjoc.18.124

• , entries 1 and 4). Application of ligand (S,S)-methyl-DUPHOS (L3) gave increased ee in the hydrogenation reaction, but the best result (90% ee) was achieved using 6 mol % Josiphos ligand L2 at 35 °C. Following the synthesis of 3-propylnorleucin methyl ester (16a), we carried on with the amine couplings

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• ][4]. A heterocyclic ring containing a P atom appears in many popular P(III)-ligands, such as BPE, DuPhos, TangPhos, DuanPhos, ZhangPhos [5][6][7][8][9][10][11], among which a number of species may be considered as privileged ligands for transition metal-catalyzed enantioselective transformations [12

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• 219. Based on the type of ligands used (e.g., Me-DuPhos; L24 vs. Cy3P), either vinyl (220–223) or allylic (224–228) silanes could be obtained, respectively, in good yields. Different types of substrates were studied to give maximum selectivity for the desired product (Scheme 38). Also, for cases

• have been reported to take place in high yields, along with high diastereo- and enantioselectivities. Applications of optimized ligands, such as (R,R)-QuinoxP* and (R,R)-iPr-DuPhos, for borylation of (E)-allylic phosphates 334 delivers either the trans or cis-configuration of these cyclopropyl moieties

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• reaction (Scheme 8) [22]. This reaction involved the intramolecular cyclization of 27 to form 28. A variety of phosphines were examined as the catalyst, and (S,S)-29 ((S,S)-Me-DuPhos, 0.1 equivalent) was found to provide the best combination of reactivity and stereoselectivity (39% yield, 62% ee). In these

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• )-selective Wittig–Horner reaction with phosphonate 66 [111] in order to obtain the didehydro amino acid 67. The next important step of this route was an asymmetric catalytic hydrogenation [112][113] with the chiral Rh(I)–DuPHOS catalyst 68 to prepare the (6'S)-configured product 69 [109][110]. Subsequent

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

NAA-modified DNA oligonucleotides with zwitterionic backbones: stereoselective synthesis of A–T phosphoramidite building blocks

• Boris Schmidtgall,
• Claudia Höbartner and
• Christian Ducho

Beilstein J. Org. Chem. 2015, 11, 50–60, doi:10.3762/bjoc.11.8

• was therefore decided to use the aforementioned mixture of double bond isomers (containing 9% of the unwanted E-isomer) as starting material for this transformation. Asymmetric hydrogenation reactions were performed under homogeneous conditions using the chiral catalysts (S,S)-Me-DuPHOS-Rh or (R,R)-Me

• -DuPHOS-Rh, respectively [59]. It is known that asymmetric hydrogenations of Z-configured didehydro amino acids catalyzed by (S,S)-Me-DuPHOS-Rh give L-amino acids and that analogous reactions catalyzed by (R,R)-Me-DuPHOS-Rh provide D-amino acids [57][60]. This has also been observed when these catalysts

• )-protected Z-17 in the presence of (S,S)-Me-DuPHOS-Rh thus furnished thymidine-derived nucleosyl amino acid (S)-19 in 94% yield, and its 6'-epimer (R)-19 was obtained from the same starting material in 99% yield using catalytic amounts of (R,R)-Me-DuPHOS-Rh (Table 1, entries 1 and 2). Both transformations

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• various aspartic acid derivatives. Using the commercially available chiral catalyst (S,S)-Et-Duphos E7, Loh and co-workers developed the asymmetric [3 + 2] annulations of phenyl allenone and furanyl allenone with electron-deficient olefins, namely enones, maleates, and fumarates, to give corresponding

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• derivatives and acrylate esters 44) in the presence of Pt((R,R)-Me-DuPhos) complexes (Scheme 14). However, the products 45 suffered from low enantioselectivities [121]. The mode of action is based on the activation of the P-nucleophile. The proposed mechanism includes the P–H oxidative addition to platinum

• phosphine–borane complex 13b (Scheme 23) [165]. Chiral phosphines with a C-stereogenic center have been studied but this was the first attempt for the asymmetric synthesis of a P-stereogenic compound. After evaluating several conditions the best catalyst was (S,S)-Me-DuPhos (46). An enantioenriched

A two step synthesis of a key unit B precursor of cryptophycins by asymmetric hydrogenation

• Benedikt Sammet,
• Mathilde Brax and
• Norbert Sewald

Beilstein J. Org. Chem. 2011, 7, 243–245, doi:10.3762/bjoc.7.32

• yields from commercially available starting materials has been developed. The key step is an asymmetric hydrogenation using the commercially available [(COD)Rh-(R,R)-Et-DuPhos]BF4 catalyst. The synthetic route provides the advantage of less synthetic steps, proceeds with high yields and

• enantioselectivity, and avoids hazardous reaction conditions. Keywords: amino acid; asymmetric hydrogenation; cryptophycin; DuPhos; Introduction Cryptophycins are macrocyclic depsipeptides, which show very high cytotoxicity even against multidrug-resistant cell lines. They inhibit mitosis of eukaryotic cells by

• developed synthesis 3-chloro-4-methoxybenzaldehyde is reacted with rac-Boc-α-phosphonoglycine trimethyl ester (9) [13][14] to yield olefin 10 in a completely Z-selective Horner–Wadsworth–Emmons (HWE) reaction (Scheme 3). Asymmetric hydrogenation using the commercially available [(COD)Rh-(R,R)-Et-DuPhos]BF4