Biomimetic Synthesis of Chejuenolides A–C by a Cryptic Lactone-Based Macrocyclization: Stereochemical Implications in Biosynthesis

A hypothetical Mannich macrocyclization in the biosynthesis of chejuenolides A–C served as the basis for the synthetic design herein. Using a lactone-based linear precursor constructed via a tactic sequence of aldol–Julia–aldol reactions on a gram scale, the biomimetic total synthesis and structural validation of chejuenolides A–C were successfully achieved for the first time. The β-oxo-δ-lactone unit in the macrocyclized adducts was fragile and readily converted to a series of C2/C18-diastereoisomers via a decarboxylation and protonation pathway. Stereochemical identification of the biosynthetic precursor (O3P2) confirmed structural adherence to the given macrocycles and previously clarified lankacidins. Moreover, the stereovariants of the linear precursor designed for the macrocyclization event highlighted the unparalleled impact of using this biomimetic approach to determine the stereoselectivity in the proposed enzymatic reaction by reviving the lost or unstable intermediate

Biomimetic Synthesis of Chejuenolides A–C by a Cryptic Lactone-Based Macrocyclization: Stereochemical Implications in Biosynthesis

A hypothetical Mannich macrocyclization in the biosynthesis of chejuenolides A–C served as the basis for the synthetic design herein. Using a lactone-based linear precursor constructed via a tactic sequence of aldol–Julia–aldol reactions on a gram scale, the biomimetic total synthesis and structural validation of chejuenolides A–C were successfully achieved for the first time. The β-oxo-δ-lactone unit in the macrocyclized adducts was fragile and readily converted to a series of C2/C18-diastereoisomers via a decarboxylation and protonation pathway. Stereochemical identification of the biosynthetic precursor (O3P2) confirmed structural adherence to the given macrocycles and previously clarified lankacidins. Moreover, the stereovariants of the linear precursor designed for the macrocyclization event highlighted the unparalleled impact of using this biomimetic approach to determine the stereoselectivity in the proposed enzymatic reaction by reviving the lost or unstable intermediate

Biomimetic Synthesis of Chejuenolides A–C by a Cryptic Lactone-Based Macrocyclization: Stereochemical Implications in Biosynthesis

A hypothetical Mannich macrocyclization in the biosynthesis of chejuenolides A–C served as the basis for the synthetic design herein. Using a lactone-based linear precursor constructed via a tactic sequence of aldol–Julia–aldol reactions on a gram scale, the biomimetic total synthesis and structural validation of chejuenolides A–C were successfully achieved for the first time. The β-oxo-δ-lactone unit in the macrocyclized adducts was fragile and readily converted to a series of C2/C18-diastereoisomers via a decarboxylation and protonation pathway. Stereochemical identification of the biosynthetic precursor (O3P2) confirmed structural adherence to the given macrocycles and previously clarified lankacidins. Moreover, the stereovariants of the linear precursor designed for the macrocyclization event highlighted the unparalleled impact of using this biomimetic approach to determine the stereoselectivity in the proposed enzymatic reaction by reviving the lost or unstable intermediate

Biomimetic Synthesis of Chejuenolides A–C by a Cryptic Lactone-Based Macrocyclization: Stereochemical Implications in Biosynthesis

A hypothetical Mannich macrocyclization in the biosynthesis of chejuenolides A–C served as the basis for the synthetic design herein. Using a lactone-based linear precursor constructed via a tactic sequence of aldol–Julia–aldol reactions on a gram scale, the biomimetic total synthesis and structural validation of chejuenolides A–C were successfully achieved for the first time. The β-oxo-δ-lactone unit in the macrocyclized adducts was fragile and readily converted to a series of C2/C18-diastereoisomers via a decarboxylation and protonation pathway. Stereochemical identification of the biosynthetic precursor (O3P2) confirmed structural adherence to the given macrocycles and previously clarified lankacidins. Moreover, the stereovariants of the linear precursor designed for the macrocyclization event highlighted the unparalleled impact of using this biomimetic approach to determine the stereoselectivity in the proposed enzymatic reaction by reviving the lost or unstable intermediate

Biomimetic Synthesis of Chejuenolides A–C by a Cryptic Lactone-Based Macrocyclization: Stereochemical Implications in Biosynthesis

A hypothetical Mannich macrocyclization in the biosynthesis of chejuenolides A–C served as the basis for the synthetic design herein. Using a lactone-based linear precursor constructed via a tactic sequence of aldol–Julia–aldol reactions on a gram scale, the biomimetic total synthesis and structural validation of chejuenolides A–C were successfully achieved for the first time. The β-oxo-δ-lactone unit in the macrocyclized adducts was fragile and readily converted to a series of C2/C18-diastereoisomers via a decarboxylation and protonation pathway. Stereochemical identification of the biosynthetic precursor (O3P2) confirmed structural adherence to the given macrocycles and previously clarified lankacidins. Moreover, the stereovariants of the linear precursor designed for the macrocyclization event highlighted the unparalleled impact of using this biomimetic approach to determine the stereoselectivity in the proposed enzymatic reaction by reviving the lost or unstable intermediate

Biomimetic Synthesis of Chejuenolides A–C by a Cryptic Lactone-Based Macrocyclization: Stereochemical Implications in Biosynthesis

A hypothetical Mannich macrocyclization in the biosynthesis of chejuenolides A–C served as the basis for the synthetic design herein. Using a lactone-based linear precursor constructed via a tactic sequence of aldol–Julia–aldol reactions on a gram scale, the biomimetic total synthesis and structural validation of chejuenolides A–C were successfully achieved for the first time. The β-oxo-δ-lactone unit in the macrocyclized adducts was fragile and readily converted to a series of C2/C18-diastereoisomers via a decarboxylation and protonation pathway. Stereochemical identification of the biosynthetic precursor (O3P2) confirmed structural adherence to the given macrocycles and previously clarified lankacidins. Moreover, the stereovariants of the linear precursor designed for the macrocyclization event highlighted the unparalleled impact of using this biomimetic approach to determine the stereoselectivity in the proposed enzymatic reaction by reviving the lost or unstable intermediate

New Compressed Chalcopyrite-like Li₂BaM^IVQ₄ (M^IV = Ge, Sn; Q = S, Se): Promising Infrared Nonlinear Optical Materials

Chalcopyrite-type AgGaQ₂ (Q = S, Se) and ZnGeP₂ are the main commercial infrared nonlinear optical (IR NLO) crystals. Unfortunately, performance defects including low laser damage threshold (LDT), harmful two-photon absorption (TPA), or small birefringence limit their application. With this background, four new compressed chalcopyrite-like IR NLO materials Li₂BaM^IVQ₄ (M^IV = Ge, Sn; Q = S, Se) were successfully synthesized with the typical AgGaQ₂ as templates. Remarkably, Li₂BaGeS₄ and Li₂BaSnS₄ not only maintain the good NLO responses (0.5 and 0.7 × AgGaS₂) but also overcome low LDTs and TPA of commercial chalcopyrites, demonstrating that they satisfy critical demands as promising IR NLO candidates. All of them exhibit phase-matching abilities. Furthermore, the discovery of chalcopyrite-like compounds also provides a feasible design strategy to explore new promising IR NLO materials

MGF E peptide pretreatment improves collagen synthesis and cell proliferation of injured human ACL fibroblasts via MEK-ERK1/2 signaling pathway

<p>Injured anterior cruciate ligament (ACL) is hard to heal due to the poor proliferative potential of ACL fibroblasts. To verify whether mechano-growth factor (MGF) E peptide can restore the cell proliferation of injured ACL fibroblasts, ACL fibroblasts pretreated with MGF E peptide were subjected to injurious stretch and the outcomes were evaluated at 0 and 24 h. After injured, the type III collagen synthesis was increased at 0 h while inhibited at 24 h. The matrix metalloproteinase-2 (MMP-2) activity/expression was up-regulated, but the cell proliferation was inhibited. Fortunately, exogenous MGF E peptide decreased the type I/III collagen synthesis at 0 h but improved the type III collagen synthesis at 24 h. It decreased the MMP-2 activity/expression of injured ACL fibroblasts. Besides, MGF E peptide accelerated the cell proliferation <i>via</i> MEK-ERK1/2 signaling pathway. Our results implied that MGF E peptide pretreatment could provide a new efficient approach for ACL regeneration.</p

Advantageous Units in Antimony Sulfides: Exploration and Design of Infrared Nonlinear Optical Materials

The exploration of infrared (IR) nonlinear optical (NLO) materials remains attractive because of the urgent requirements in the laser field. Meanwhile, the deepened cognition of structure–property relationships is necessary to help guide the exploration of IR NLO materials. So far, the family of antimony sulfides is an important system with a lot of attention, and a series of antimony sulfides are reported. However, it is urgent to reveal how different Sb–S units, like SbS₃, SbS₄, and more complex combinations, affect apparent properties. Here, taking ternary metal antimony sulfides as examples, the sources of some essential optical properties, such as second harmonic generation (SHG) and birefringence, are systematically analyzed through first-principles calculations, and the mechanisms of the performances with various magnitudes are also presented to clarify the structure–property relationships. The results indicate that the SbS₄ unit among antimony sulfides is an advantageous NLO-active unit, which can balance the contradiction between the band gap and SHG response. Introduction of transition metals in the Sb–S anionic frameworks can tune the magnitude of birefringence. Besides, the substitution of a cation from a transition metal to an alkali metal can notably enlarge the band gap and maintain a large SHG response. These design strategies are beneficial to explore potential IR NLO materials with Sb–S units

A Member of Fluorooxoborates: Li₂Na_0.9K_0.1B₅O₈F₂ with the Fundamental Building Block B₅O₁₀F₂ and a Short Cutoff Edge

A new member of fluorooxoborates, Li₂Na_0.9K_0.1B₅O₈F₂, was obtained in the sealed system, and single-crystal X-ray diffraction was used to determine its structure. It contains a three-dimensional framework stacking of [B₅O₈F₂]^3– layers extending into the <i>ac</i> plane. Detailed structural comparisons among all of the fluorine-containing alkali-metal borates suggest that the [B₅O₈F₂]^3– layer composed of the new fundamental building blocks B₅O₁₀F₂ represents a new structure type of fluorooxoborate. The IR spectrum verifies its structural validity. The deep-ultraviolet spectral measurement shows that it has no obvious absorption in the range of 180–300 nm, and its cutoff edge is under 180 nm. In addition, theoretical calculations were done to help us understand its electronic structure and optical properties