Highly stereoselective transformation of (1S,3S)-cis-1,3-disubstituted tetrahydro-β-carbolines into (1S,3R)-trans-1,3-disubstituted tetrahydro-β-carbolines: an improved asymmetric synthesis of tadalafil from l-tryptophan

Development of potent and selective tetrahydro-β-carboline-based HDAC6 inhibitors with promising activity against triple-negative breast cancer

Overexpression of histone deacetylase 6 (HDAC6) is implicated in tumorigenesis, invasion, migration, survival, apoptosis, and growth of various malignancies, making it a promising target for cancer treatment. Building on our previous work, we report a novel series of tetrahydro-β-carboline-piperazinedione derivatives as HDAC6 inhibitors. Structural modifications were introduced at the 6-aryl group, with the m-bromophenyl derivative (9c) emerging as the most potent HDAC6 inhibitor, exhibiting an IC50 of 7 nM. Compound 9c demonstrated robust growth inhibitory activity across 60 cancer cell lines from the NCI panel, with a mean GI50 of 2.64 μM and a GI50 below 5 μM for nearly all tested lines, while exhibiting significantly lower cytotoxicity towards non-tumor cell lines. The triple-negative breast cancer cell line MDA-MB-231 was selected for further investigation of 9c's cellular effects. 9c selectively increased the acetylation of non-histone α-tubulin in MDA-MB-231 cells, confirming its HDAC6 selectivity. Furthermore, 9c effectively induced apoptosis, caused apoptotic sub-G1 phase accumulation, upregulated pro-apoptotic caspase-3, and downregulated anti-apoptotic Bcl-2. Notably, 9c reduced the expression of programmed death-ligand 1 (PD-L1), a key immune checkpoint protein that enables tumor cells to evade immune surveillance, highlighting its potential role in enhancing anti-tumor immunity. In addition, 9c inhibited phosphorylated extracellular signal-regulated kinase (ERK)1/2, a central signaling pathway that drives cell proliferation, survival, and migration, further highlighting its significance in suppressing tumor progression and growth. In migration assays, 9c impaired cell motility, achieving 80% gap closure inhibition in a wound-healing assay. Collectively, these findings underline compound 9c as a highly promising candidate for the treatment of triple-negative breast cancer, with the added benefits of PD-L1 and ERK inhibition for potential synergy in enhancing anti-tumor immunity and reducing tumor cell proliferation.

Novel practical stereoselective synthesis of a bicyclic hydantoino-thiolactone as the key intermediate for production of (+)-biotin

Bicyclic hydantoinothiolactone (1), as the key intermediate for production of (+)-biotin, has been efficiently and high-stereoselectively synthesized from the cheap starting material l-cystine via nine steps in 44% overall yield. In this new practical synthesis, there are two characteristic steps worthy of note. One step is TMSOTf-catalyzed efficient cyanation of (3S,7aR)-6-benzyl-5-oxo-3-phenyltetrahydro-1H,3H-imidazo[1,5-c]thiazol-7-yl acetate, the other step is DBU-catalyzed rapid isomerization of trans-isomer to cis-isomer of the bicyclic hydantoinothiolactone.

TCCA-mediated oxidative rearrangement of tetrahydro-β-carbolines: facile access to spirooxindoles and the total synthesis of (±)-coerulescine and (±)-horsfiline

Multi-reactive centered reagents are beneficial in chemical synthesis due to their advantage of minimal material utilization and formation of less by-products. Trichloroisocyanuric acid (TCCA), a reagent with three reactive centers, was employed in the synthesis of spirooxindoles through the oxidative rearrangement of various N-protected tetrahydro-β-carbolines. In this protocol, low equivalents of TCCA were required to access spirooxindoles (up to 99% yield) with a wide substrate scope. Furthermore, the applicability and robustness of this protocol were proven for the gram-scale total synthesis of natural alkaloids such as (±)-coerulescine (1) and (±)-horsfiline (2) in excellent yields.

Three-reactive centered reagent (TCCA) mediated construction of spirooxindoles through an oxidative rearrangement of various N-protected tetrahydro-β-carbolines and total synthesis of natural alkaloids (±)-coerulescine and (±)-horsfiline.

Tailor-made amino acids in the design of small-molecule blockbuster drugs

The role of amino acids (AAs) in modern health industry is well-appreciated. Residues of individual AAs, or their chemical modifications, such as diamines and amino alcohols, are frequently found in the structures of modern pharmaceuticals. The goal of this review article, is to emphasize that, currently, tailor-made AAs serve as key structural features in many most successful pharmaceuticals, so-called blockbuster drugs. In the present article, we profile 14 small-molecule drugs, underscoring the breadth of structural variety of AAs applications in numerous therapeutic areas. For each compound, we provide spectrum of biological activity, medicinal chemistry discovery, and synthetic approaches.

Highly diastereoselective crystallization-induced asymmetric transformation of 1,3-disubstituted-tetrahydro-β-carbolines in water

A green and highly stereoselective method for the synthesis of cis or trans-1,3-disubstituted-tetrahydro-β-carbolines has been developed using water as the solvent.