HSP90 is a member of the family of heat shock proteins responsible for folding proteins into mature conformations and thus maintaining their biological function in cells. Since it is involved in all hallmarks of cancer, HSP90 has been considered as a promising drug target for cancer therapy. Eighteen HSP90 inhibitors have entered clinical trials, however, none has been approved by the FDA. There is still a great need for novel HSP90 inhibitors with strong anticancer activity and good safety profile. In the past several years, many new molecules were identified as HSP90 inhibitors and some of them have shown promising pharmacological profiles in preclinical evaluations. In this review, HSP90 inhibitors identified from 2014 to date are summarized and their design strategies, chemical structures, and biological activities are reviewed. The inhibitors are categorized by their different target domains and selectivity as N-terminal, C-terminal, and isoform-selective HSP90 inhibitors.

Phenols and aryl thiols are fundamental building blocks in organic synthesis and final products with interesting biological activities. Over the past decades, substantial progress has been made in transition-metal-catalyzed coupling reactions, which resulted in the emergence of new methods for the synthesis of phenols and aryl thiols. Aryl halides have been extensively studied as substrates for the synthesis of phenols and aryl thiols. In very recent years, C–H activation represents a powerful strategy for the construction of functionalized phenols directly from various arenes. However, the synthesis of aryl thiols through C–H activation has not been reported. In this review, a brief overview is given of the recent advances in synthetic strategies for both phenols and aryl thiols.

Nano-graphene oxide (NGO) has been proposed as a novel drug carrier. However, its poor biocompatibility and physiological stability as well as the lack of cancer targeting ability have limited its further application in cancer therapy. To solve this problem, we developed a novel nanohybrid, NGO/DOX@SPC-FA, by first allowing a soy phosphatidylcholine (SPC) membrane to encapsulate DOX-loaded NGO (NGO/DOX) and then modifying the SPC membrane with a PEGylated lipid–FA conjugate to achieve the presentation of cancer targeting folic acid (FA) on the nanohybrid surface. The SPC membrane (mimicking cell membrane) endowed the resultant nanohybrids (NGO/DOX@SPC-FA) with good stability and biocompatibility, high drug loading capability, efficient cellular uptake, and controlled drug release. Moreover, compared with NGO/DOX and SPC-modified NGO/DOX (NGO/DOX@SPC), the FA-modified NGO/DOX@SPC nanohybrids (NGO/DOX@SPC-FA) could deliver NGO/DOX to cancer cells with improved delivery and killing efficacy due to the presence of FA targeting motifs on their surface. The NGO/DOX@SPC-FA nanohybrids were found to be internalized specifically by FA-positive cancer cells (HeLa cells) through both macropinocytosis-directed engulfment and clathrin-dependent endocytosis, and then become localized into lysosomes. The in vivo biodistribution study showed that NGO/DOX@SPC-FA had high tumor targeting ability because of the active targeting mechanism with FA modification. The in vivo antitumor therapy study demonstrated that NGO/DOX@SPC-FA could significantly inhibit tumour growth and prolong the survival time of mice. Our results suggested that NGO/DOX@SPC-FA, as a novel drug delivery system with high drug loading and targeted delivery efficiency, holds promise for future cancer therapy.

A facile and effective C–H functionalization strategy for the synthesis of 2-mercaptobenzothiazoles and 2-mercaptobenzoxazoles is described. 1,3-Propanedithiol was employed to convert benzothiazoles and benzoxazoles to the corresponding heteroarylthiols in the presence of potassium hydroxide and DMSO. This novel protocol is featured by direct C–H mercaptalization of heteroarenes and a simple reaction system.

A copper-catalyzed direct and effective synthesis of aryl thiols from aryl iodides using readily available Na₂S·9H₂O and 1,2-ethanedithiol was described. A variety of aryl thiols were readily obtained in yields of 76–99%. In this protocol, Na₂S·9H₂O was used as ultimate sulfur source, and 1,2-ethanedithiol functioned as an indispensable catalytic reagent.