Design, Synthesis, and Evaluation of a Series of Novel Benzocyclobutene Derivatives as General Anesthetics

Asymmetric Synthesis of Scillascillin-Type Homoisoflavonoid

The first asymmetric synthesis of a scillascillin-type homoisoflavonoid was reported. Key reactions for the asymmetric synthesis of benzocyclobutene include catalytic reductive desymmetrization of malonic ester and an intramolecular C-H activation of the methyl group.

Palladium-Catalyzed Skeletal Rearrangement of Substituted 2-Silylaryl Triflates via 1,5-C-Pd/C-Si Bond Exchange

A palladium-catalyzed skeletal rearrangement of 2-(2-allylarylsilyl)aryl triflates has been developed to give highly fused tetrahydrophenanthrosilole derivatives via unprecedented 1,5-C-Pd/C-Si bond exchange. The reaction pathways can be switched toward 4-membered ring-forming C(sp2 )-H alkylation by tuning the reaction conditions to give completely different products, fused dihydrodibenzosilepin derivatives, from the same starting materials. The inspection of the reaction conditions revealed the importance of carboxylates in promoting the C-Pd/C-Si bond exchange.

Drug-drug interaction study of ciprofol and sodium divalproex: Pharmacokinetics, pharmacodynamics, and safety in healthy Chinese subjects

Ciprofol (also known as HSK3486) is a promising intravenous anesthetic candidate derived from propofol and independently developed by Haisco Pharmaceutical Group Co., Ltd. (Chengdu, China). Compared with propofol, ciprofol has the potential to reduce the dose required and the associated risks. Ciprofol is extensively metabolized in vivo, and its interaction with other concurrently administered drugs during clinical application is worthy of attention. Therefore, an open-label, two-stage sequential study was performed in healthy subjects who received either a single administration of ciprofol injection or ciprofol injection after oral administration of sodium divalproex. The aim of the study was to evaluate the effects of sodium divalproex on ciprofol with respect to pharmacokinetics, pharmacodynamics, and safety, thus providing a basis for the rational clinical use of ciprofol and sodium divalproex.

Ciprofol: A Novel Alternative to Propofol in Clinical Intravenous Anesthesia?

Ciprofol is a novel compound that was independently developed in China. According to the Chinese product instructions approved by the China National Medical Products Administration and the information of official website, indications for ciprofol include sedation and anesthesia during the surgical/procedure of nontracheal intubation, induction and maintenance of general anesthesia, and sedation during intensive care. Ciprofol is a short-acting intravenous sedative based on the structural modification of propofol. Ciprofol has high efficacy, good selectivity, and fewer adverse reactions, indicating good clinical application potential. A series of clinical studies have been conducted to evaluate the sedative effect of ciprofol in various procedures and settings, including gastroscopy and colonoscopy, fiber-optic bronchoscopy, general anesthesia in elective surgeries, and mechanical ventilation in intensive care units. This review summarizes the chemical structure, pharmacodynamics, and pharmacokinetic properties of ciprofol. We also assessed the efficacy and safety of ciprofol by synthesizing the relevant clinical trial data.

Synergistic Brønsted/Lewis acid catalyzed aromatic alkylation with unactivated tertiary alcohols or di-tert-butylperoxide to synthesize quaternary carbon centers

Dual Brønsted/Lewis acid catalysis involving environmentally benign, readily accessible protic acid and iron promotes site-selective tert-butylation of electron-rich arenes using di-tert-butylperoxide. This transformation inspired the development of a synergistic Brønsted/Lewis acid catalyzed aromatic alkylation that fills a gap in the Friedel-Crafts reaction literature by employing unactivated tertiary alcohols as alkylating agents, leading to new quaternary carbon centers. Corroborated by DFT calculations, the Lewis acid serves a role in enhancing the acidity of the Brønsted acid. The use of non-allylic, non-benzylic, and non-propargylic tertiary alcohols represents an underexplored area in Friedel-Crafts reactivity.

CYCLOBUTANES IN SMALL MOLECULE DRUG CANDIDATES

Cyclobutanes are increasingly used in medicinal chemistry in the search for relevant biological properties. Important characteristics of the cyclobutane ring include its unique puckered structure, longer C−C bond lengths, increased C−C π‐character and relative chemical inertness for a highly strained carbocycle. This review will focus on contributions of cyclobutane rings in drug candidates to arrive at favorable properties. Cyclobutanes have been employed for improving multiple factors such as preventing cis/trans‐isomerization by replacing alkenes, replacing larger cyclic systems, increasing metabolic stability, directing key pharmacophore groups, inducing conformational restriction, reducing planarity, as aryl isostere and filling hydrophobic pockets.

Catalytic enantioselective synthesis of benzocyclobutenols and cyclobutanols via a sequential reduction/C-H functionalization

We report here a sequential enantioselective reduction/C-H functionalization to install contiguous stereogenic carbon centers of benzocyclobutenols and cyclobutanols. This strategy features a practical enantioselective reduction of a ketone and a diastereospecific iridium-catalyzed C-H silylation. Further transformations have been explored, including controllable regioselective ring-opening reactions. In addition, this strategy has been utilized for the synthesis of three natural products, phyllostoxin (proposed structure), grandisol and fragranol.

Opportunities for Tapping into Three-Dimensional Chemical Space through a Quaternary Carbon

A quaternary carbon bears four other carbon substituents or combination of four non-hydrogen substituents at four vertices of a tetrahedron. The spirocyclic quaternary carbon positioned at the center of a bioactive molecule offers conformational rigidity, which in turn reduces the penalty for conformational entropy. The quaternary carbon is a predominant feature of natural product structures and has been associated with more effective and selective binding to target proteins compared to planar compounds with a high sp² count. The presence of a quaternary carbon stereocenter allows the exploration of novel chemical space to obtain new molecules with enhanced three-dimensionality. These characteristics, coupled to an increasing awareness to develop sp³-rich molecules, boosted utility of quaternary carbon stereocenters in bioactive compounds. It is hoped that this Perspective will inspire the chemist to utilize quaternary carbon stereocenters to enhance potency, selectivity, and other drug-like properties.

Alder-ene reactions driven by high steric strain and bond angle distortion to form benzocyclobutenes

A unique aryne-based Alder-ene reaction to form benzocyclobutene is described.

A unique aryne-based Alder-ene reaction to form benzocyclobutene is described. In this process, the thermodynamic barrier to form a four-membered ring is compensated by the relief of the strain energy of an aryne intermediate. On the other hand, the driving force to overcome the high kinetic barrier is provided by the gearing effect of the bulky substituent at the ortho-position of the ene-donor alkene. To maximize the steric strain by the ortho-substituent, a structural element for internal hydrogen bonding is installed, which plays a crucial role for both the hexadehydro Diels–Alder and the Alder-ene reactions. DFT calculations show that the bulky hydrogen bonding element lowers the activation barrier for the Alder-ene reaction by destabilizing the intermediate, which is due to the severe bond angle distortion. The preferred formation of cis-isomers can also be explained by the extent of bond angle distortion.

Synthetic Approach to Benzocyclobutenones Using Visible Light and a Phosphonate Auxiliary

Reported herein is a two-step procedure to synthesize benzocyclobutenones from (o-alkylbenzoyl)phosphonates. It consists of a visible-light-driven cyclization reaction forming phosphonate-substituted benzocyclobutenols and subsequent elimination reaction of the H-phosphonate, which assumes a key role as the recyclable auxiliary. A wide variety of functionalized benzocyclobutenones, which include those difficult to synthesize by conventional methods, are efficiently synthesized.