First total synthesis of the 2,7-naphthyridine alkaloid neozeylanicine and unexpected formation of isoquinolines from ethoxyvinyl pyridines

A novel approach to 2-arylmethyl-2,3-dihydro-4(1H)-quinazolinones. Total synthesis of the alkaloids glycozolone-A and glycozolone-B

2-Arylmethyl-2,3-dihydro-4(1H)-quinazolinones are a small subgroup of the class of quinazolin-4-one alkaloids, and most published total syntheses require the use of unstable and poorly accessible arylacetaldehydes. Here we show that easily available, stable ω-methoxystyrenes are versatile substitutes for arylacetaldehydes. This new methodology was applied to the total synthesis of the alkaloids glycozolone-A and glycozolone-B. The limitations of this new approach were analyzed as well. In this course, new total syntheses of two 2-arylmethyl-4(1H)-quinazolinone alkaloids (glycosminine, 2-(4-hydroxybenzyl)-4(1H)-quinazolinone) were developed as well.

Synthesis and Anticancer Properties of Functionalized 1,6-Naphthyridines

The burgeoning interest in synthesis and biological applications of 1,6-naphthyridines reflects the importance of 1,6-naphthyridines in the synthetic as well as medicinal chemistry fields. Specially, 1,6-naphthyridines are pharmacologically active, with variety of applications such as anticancer, anti-human immunodeficiency virus (HIV), anti-microbial, analgesic, anti-inflammatory and anti-oxidant activities. Although collective recent synthetic developments have paved a path to a wide range of functionalized 1,6-naphthyridines, a complete correlation of synthesis with biological activity remains elusive. The current review focuses on recent synthetic developments from the last decade and a thorough study of the anticancer activity of 1,6-naphthyridines on different cancer cell lines. Anticancer activity has been correlated to 1,6-naphthyridines using the literature on the structure-activity relationship (SAR) along with molecular modeling studies. Exceptionally, at the end of this review, the utility of 1,6-naphthyridines displaying activities other than anticancer has also been included as a glimmering extension.

A Short Synthesis of the Plant Alkaloid 4-Methyl-2,6-naphthyridine

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A new synthesis of the 2,6-naphthyridine alkaloid 4-methyl-2,6-naphthyridine from Antirrhinum majus has been developed. Key steps are a regioselective oxidation of 3-bromo-4,5- dimethylpyridine to the corresponding 4-formyl derivative, and the annulation of the second pyridine ring by Suzuki-Miyaura cross-coupling using (E)-2-ethoxyvinylboronic acid pinacol ester as a masked acetaldehyde equivalent. This protocol gives the alkaloid in four steps starting from commercially available 3,4-dimethylpyridine in 15% overall yield. This annulation protocol should be useful for the synthesis of other condensed pyridines as well.

First total synthesis of the 2,7-naphthyridine alkaloids lophocladine a and B

The one-pot reaction of 4-benzylpyridine-3-carbonitrile with Bredereck's reagent and subsequent treatment with either glacial acetic acid and sulfuric acid or ammonium acetate provided the new bioactive naphthyridine alkaloids lophocladine A and B, respectively.

Synthesis and conformational dynamics of tricyclic pyridones containing a fused seven-membered ring

A new synthetic approach to tricyclic pyridones bearing a fused seven-membered ring is described. These compounds exhibit atropisomerism and exist in enantiomeric forms. Chiral HPLC separation of the enantiomers has allowed the rates of racemization to be measured and hence the free energy barrier for flipping the seven-membered ring to be deduced. Introduction of a further element of planar chirality leads to diastereomeric atropisomerism. The rate of interconversion of the diastereomers has been quantified by 2D EXSY NMR spectroscopy allowing a full description of the conformational dynamics of the system.