Marine natural products offer an abundant source of pharmacologically active agents with great diversity and complexity, and the potential to produce valuable therapeutic entities. Indole alkaloids is one of the important class of marine-derived secondary metabolites, with wide occurrence amongst variety of marine sources such as sponges, tunicates, algae, worms and microorganisms and have been extensively studied for their biological activities. Among this chemical family, a sponge-derived bis-indole alkaloid fascaplysin (1) exhibited broad range of bioactivities including antibacterial, antifungal, antiviral, anti-HIV-1-RTase, p56 tyrosine kinase inhibition, antimalarial, anti-angiogenic, antiproliferative activity against numerous cancer cell lines, specific inhibition of cyclin-dependent kinase-4 (IC(50) 350 nM) and action as a DNA intercalator. In the present review, the chemical diversity of natural as well as synthetic analogues of fascaplysin has been reviewed with a detailed account on synthetic reports and pharmacological studies. Our analysis of the structure-activity relationships of this family of compounds highlights the existence of various potential leads for the development of novel anticancer agents.

No abstract

No abstract

No abstract

No abstract

No abstract

Novel reactions under Pictet-Spengler conditions between tryptophan methyl ester/tryptamine and 2-oxoaldehydes have been developed and successfully utilized for the total synthesis of Merinacarboline (A and B), Eudistomin Y1, Pityriacitrin B, Pityriacitrin, Fascaplysin and analogues.2-Oxoaldehydes (OA) are among a few precursors that have been used extensively to synthesize a large variety of heterocyclic compounds. 1 Pictet-Spengler is one of the various reactions reported on OA leading to the synthesis of b-carbolines. 2-11 A large number of naturally occurring b-carbolines with acyl substitution at the C-1 position have shown promising antiinammatory, 2 anti-malarial, 12 anti-cancer, 3,13 anti-phospholipase A2, 14 anti-microbial, 15 and anti-bacterial activities. 16 In view of these biochemical observations, convenient synthetic methods for the synthesis of such constructs are desirable. Even though the Pictet-Spengler reaction of tryptamine/tryptophan/ tryptophan methyl ester with OA for generation of 1-substituted b-carbolines has been explored, 2,6 a few areas are still untouched. As we know in contemporary organic synthesis, coupled domino reactions, wherein two or more domino processes occur sequentially in the same reaction, are considered to be most effective for the synthesis of complex organic compounds using simple and readily available building blocks. 17,18 In this context, we developed a few unexplored reactions between tryptophan methyl ester/tryptamine and 2-oxoaldehydes with a focus on establishing a multicoupled domino strategy for the synthesis of various marine based natural products and their analogues.We initiated the present study with a reaction of 2,4-dimethoxy acetophenone 1 with tryptophan methyl ester 2 in the presence of iodine in DMSO. The reaction of 1 (1 equiv.) and 2 (1 equiv.) with I 2 (1 equiv.) in DMSO at 90 C for 1.5 h afford the desired product in low yield (38%, Table 1, entry 15). To improve upon the yields of desired product, a preliminary set of reactions between tryptophan methyl ester (1 equiv.) and acetophenone (1 equiv.) under different condition were carried out (Table 1). Table 1 Optimization studies for synthesis of 3a employing 2,4-dimethoxy acetophenone as building block a Entry (Equiv.) Temp. Time Yield b (%)

Novel quinazolonthiazoles were designed and synthesized as new potential antimicrobial agents by facile multi-step procedure from o-aminobenzoic acids and 2-acetylthiazole. A series of biological evaluation showed that compound 7d was the most effective quinazolonethiazole with superior activity to reference drugs chloramphenicol and norfloxacin. This active molecule displayed unobvious bacterial resistance against P. aeruginosa, the low toxicity to normal hepatocytes, suitable pharmacokinetics and drug-likeness. The preliminary biological interaction suggested that quinazolonethiazole 7d might induce bacterial death by disturbing the membrane permeability, whilst preventing bacteria from growth by integrating into DNA and binding with topoisomerase IV. These findings provided significant background for the further development of quinazolonethiazoles as new potential drugs in combating drug-resistant pathogens.