A Study on Land Carrying Capacity of Hunan Province

Hou, Mian; Chen, Wenjun

doi:10.1166/asl.2013.5001

Cited by 8 publications

(12 citation statements)

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“…As compared to the reaction with aryl radicals, trapping of alkyl radicals with diboron compounds is less efficient and oen requires a large excess of the diboron reagent. The trapping of primary alkyl radicals with B 2 pin 2 in DMF was reported; 56 however, for the borylation of secondary alkyl radicals under these conditions only trace product formation was achieved. In contrast, diboronic acid reacts rather efficiently with secondary alkyl radicals.…”

Section: Radical C(sp 3 )-B Bond Formationmentioning

confidence: 99%

“…In contrast, diboronic acid reacts rather efficiently with secondary alkyl radicals. 56 Presumably the most powerful reagent for the metal free borylation of alkyl radicals is B 2 cat 2 in the presence of a Lewis base (most commonly an amide based solvent), rst described by Aggarwal. 57 Even selected tertiary alkyl radicals can be borylated under these conditions.…”

Section: Radical C(sp 3 )-B Bond Formationmentioning

confidence: 99%

“…NHPI esters were also borylated by Li using a photoredox catalyst, B 2 pin 2 or B 2 (OH) 4 in DMF or a polar protic solvent mixture under visible light irradiation (Scheme 15c). 56 Alkyl radical generation is achieved by ET from the photo-excited Ir complex to the NHPI ester followed by fragmentation and loss of CO 2 . C-B bond formation occurs as discussed in Scheme 6.…”

Section: Decarboxylative Borylation (Sp 3 )mentioning

confidence: 99%

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New avenues for C–B bond formationviaradical intermediates

2019

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Section: Radical C(sp 3 )-B Bond Formationmentioning

confidence: 99%

Section: Radical C(sp 3 )-B Bond Formationmentioning

confidence: 99%

Section: Decarboxylative Borylation (Sp 3 )mentioning

confidence: 99%

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New avenues for C–B bond formationviaradical intermediates

2019

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“…1 BPin MeLi (3 equiv) , [c] NiCl 2 •6H 2 O (10 % mol), 4,4'-(MeO) 2 -bipy (13 % mol), [d] One more protocol for the decarboxylative boronation was proposed by Li and co-workers, also in 2017. [198] In this case, the reaction was carried out using Ir-based photoredox catalyst ([Ir(ppy) 2 dtbpy]PF 6 ) and B 2 pin 2 or B 2 (OH) 4 in DMF or a mixture of polar protic solvents under visible light irradiation (45 W compact fluorescent lamp, CFL). [198] The reaction is operationally simple, operates under very mild conditions, and tolerates "wet" solvents and polar functional groups, but is limited to carboxylic acids with primary or secondary alkyl side chain (Table 7, entry 4).…”

Section: # [B]mentioning

confidence: 99%

“…[198] In this case, the reaction was carried out using Ir-based photoredox catalyst ([Ir(ppy) 2 dtbpy]PF 6 ) and B 2 pin 2 or B 2 (OH) 4 in DMF or a mixture of polar protic solvents under visible light irradiation (45 W compact fluorescent lamp, CFL). [198] The reaction is operationally simple, operates under very mild conditions, and tolerates "wet" solvents and polar functional groups, but is limited to carboxylic acids with primary or secondary alkyl side chain (Table 7, entry 4). For the secondary substrates, the procedure included one-pot preparation of the corresponding trifluoroborates, whereas for the primary ones, boropinacolates were obtained.…”

Section: # [B]mentioning

confidence: 99%

Saturated Boronic Acids, Boronates, and Trifluoroborates: An Update on Their Synthetic and Medicinal Chemistry

Volochnyuk

Gorlova

Grygorenko

2021

Chemistry A European J

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This review discusses recent advances in the chemistry of saturated boronic acids, boronates, and trifluoroborates. Applications of the title compounds in the design of boron-containing drugs are surveyed, with special emphasis on α-amino boronic derivatives. A general overview of saturated boronic compounds as modern tools to construct C(sp 3 )À C and C(sp 3 )-heteroatom bonds is given, including recent developments in the Suzuki-Miyaura and Chan-Lam cross-couplings, single-electron-transfer processes including metallo-and organocatalytic photoredox reactions, and transformations of boron "ate" complexes. Finally, an attempt to summarize the current state of the art in the synthesis of saturated boronic acids, boronates, and trifluoroborates is made, with a brief mention of the "classical" methods (transmetallation of organolithium/magnesium reagents with boron species, anti-Markovnikov hydroboration of alkenes, and the modification of alkenyl boron compounds) and a special focus on recent methodologies (boronation of alkyl (pseudo)halides, derivatives of carboxylic acids, alcohols, and primary amines, boronative CÀ H activation, novel approaches to alkene hydroboration, and 1,2-metallate-type rearrangements).

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Umpolung Ala^B Reagents for the Synthesis of Non‐Proteogenic Amino Acids, Peptides and Proteins**

et al. 2022

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Non-proteogenic amino acids and functionalized peptides are important motifs in modern drug discovery. Here we report that Ala B can serve as universal building blocks in the synthesis of a diverse collection of modified amino acids, peptides, and proteins. First, we develop the synthesis of Ala B from redox-active esters of aspartic acid resulting in a series of β-boronoalanine derivatives. Next, we show that Ala B can be integrated into automated oligopeptide solidphase synthesis. Ala B is compatible with common transformations used in preparative peptide chemistry such as native chemical ligation and radical desulfurization as showcased by total synthesis of Ala B -containing ubiquitin. Furthermore, Ala B reagents participate in Pdcatalyzed reactions, including CÀ C cross-couplings and macrocyclizations. Taken together, Ala B synthons are practical reagents to access modified peptides, proteins, and in the synthesis of cyclic/stapled peptides.Peptides and proteins are important targets in modern drug discovery because of their ease of synthesis, low toxicity, and target selectivity. [1] Native peptides, however, can often show low bioavailability and short lifetimes rendering them suboptimal for clinical applications. [2] To address these challenges, non-proteogenic amino acids (NPAAs), a class of amino acids not encoded in the human genome, emerged as a valuable tool to increase structural diversity and improve pharmacokinetic properties. [3] Several strategies to access NPAAs are known including the Strecker reaction, [4] asymmetric hydrogenation, [5] conjugate addition, [6] biotransformations, [7] photoredox cross-electrophile coupling, [8] CÀ H activation, [9] and phase-transfer alkylation. [10] Access to unnatural surrogates through any of these strategies complements studies on selective modifications of biologics that can be achieved through various handles that can enable downstream functionalizations (Scheme 1A). One promising approach that can avoid competing reactions with innate groups are transformations based on umpolung of reactivity. [11] We recently reported the synthesis and applications of Ala Sn reagents in the form of carbastannatrane 1, [12] a member of a larger group of reagents where alanine's β-carbon is substituted with a metal or metalloid (Scheme 1B). Ala M reagents represent a novel type of synthons that can be engaged in cross-coupling reactions through a reversal of polarity at the β-carbon.From a conceptual standpoint, these reagents can give rise to native as well as unnatural amino acids based on a formal alanine derivatization. Several members of this family are known including organogermanium Ala Ge 2, [13] organoboron Ala B 3, [14] organosilane Ala Si 4 [14l, 15] organozinc Ala Zn 5, [16] organolithium, [14e,g] and organonickel Ala Ni[17] derivatives

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A Study on Land Carrying Capacity of Hunan Province

Cited by 8 publications

References 0 publications

New avenues for C–B bond formationviaradical intermediates

New avenues for C–B bond formationviaradical intermediates

Saturated Boronic Acids, Boronates, and Trifluoroborates: An Update on Their Synthetic and Medicinal Chemistry

Umpolung Ala^B Reagents for the Synthesis of Non‐Proteogenic Amino Acids, Peptides and Proteins**

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A Study on Land Carrying Capacity of Hunan Province

Cited by 8 publications

References 0 publications

New avenues for C–B bond formationviaradical intermediates

New avenues for C–B bond formationviaradical intermediates

Saturated Boronic Acids, Boronates, and Trifluoroborates: An Update on Their Synthetic and Medicinal Chemistry

Umpolung AlaB Reagents for the Synthesis of Non‐Proteogenic Amino Acids, Peptides and Proteins**

Contact Info

Product

Resources

About

Umpolung Ala^B Reagents for the Synthesis of Non‐Proteogenic Amino Acids, Peptides and Proteins**