Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation.

1,5-Disubstituted indole-2-carboxaldehyde derivatives 1a-h and glycine alkyl esters 2a-c are shown to undergo a novel cascade imination-heterocylization in the presence of the organic base DIPEA to provide 1-indolyl-3,5,8-substituted γ-carbolines 3aa-ea in good yields. The γ-carbolines are fluorescent and exhibit anticancer activities against cervical, lung, breast, skin, and kidney cancer cells.

Serendipitous base catalysed condensation-heteroannulation of iminoesters: a regioselective route to the synthesis of 4,6-disubstituted 5-azaindoles.

A serendipitous discovery of a novel one-pot synthesis of 4,6-disubstituted 5-azaindoles is reported herein. In the presence of Hunig's base, various N-substituted pyrrole-2-carboxaldehydes have been efficiently transformed into their corresponding 4,6-disubstituted 5-azaindoles through an imine mediated cascade condensation-heteroannulation. The synthetic value of the methodology is established by preparing a novel chemical analogue of a cannabinoid receptor type 2 (CB2) agonist.

Tyrosine-based asymmetric urea ligand for prostate carcinoma: Tuning biological efficacy through in silico studies.

In this article, we have explored the chemical interactions of tyrosine-based asymmetric urea ligands in the binding pockets of prostate specific membrane antigen (PSMA) through in silico studies. The S1 pocket of the PSMA protein offers better scope for modifications in the urea ligands to improve the binding affinity. Accordingly, tyrosine-based (S)-2-(3-((S)-1-carboxy-2-(4-(carboxymethoxy)phenyl)ethyl)ureido)pentanedioic acid (CYUE, 3) ligand was designed, synthesized and predicted to possess inhibition constant (Ki) of 55 nM with PSMA protein. The CYUE (3) ligand was further elaborated into a fluorescent diagnostic probe for detection of PSMA+ cancers. In vitro studies on human malignant cell lines such as LNCaP and PC-3 were performed to show the efficacy and specificity of the newly synthesized bio-construct. The fluorescent bio-conjugate was found to be very specific to the PSMA protein with an overall binding affinity constant (KD) of 88 nM.

Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer.

In this article, we have successfully designed and demonstrated a novel continuous process for assembling targeting ligands, peptidic spacers, fluorescent tags and a chelating core for the attachment of cytotoxic molecules, radiotracers, nanomaterials in a standard Fmoc solid-phase peptide synthesis in high yield and purity. The differentially protected Fmoc-Lys-(Tfa)-OH plays a vital role in attaching fluorescent tags while growing the peptide chain in an uninterrupted manner. The methodology is versatile for solid-phase resins that are sensitive to mild and strong acidic conditions when acid-sensitive side chain amino protecting groups such as Trt (chlorotrityl), Mtt (4-methyltrityl), Mmt (4-methoxytrityl) are employed to synthesise the ligand targeted fluorescent tagged bioconjugates. Using this methodology, DUPA rhodamine B conjugate (DUPA = 2-[3-(1,3-dicarboxypropyl)ureido]pentanedioic acid), targeting prostate specific membrane antigen (PSMA) expressed on prostate, breast, bladder and brain cancers and pteroate rhodamine B, targeting folate receptor positive cancers such as ovarian, lung, endometrium as well as inflammatory diseases have been synthesized. In vitro studies using LNCaP (PSMA +ve), PC-3 (PSMA -ve, FR -ve) and CHO-ß (FR +ve) cell lines and their respective competition experiments demonstrate the specificity of the newly synthesized bioconstructs for future application in fluorescent guided intra-operative imaging.