Traceless synthesis of 3H-quinazolin-4-ones via a combination of solid-phase and solution methodologies

Traceless Solid-Phase Organic Synthesis

Traceless solid-phase synthesis represents an ultimate sophisticated synthetic strategy on insoluble supports. Compounds synthesized on solid supports can be released without a trace of the linker that was used to tether the intermediates during the synthesis. Thus, the target products are composed only of the components (atoms, functional groups) inherent to the target core structure. A wide variety of synthetic strategies have been developed to prepare products in a traceless manner, and this review is dedicated to all aspects of traceless solid-phase organic synthesis. Importantly, the synthesis does not need to be carried out on a linker designed for traceless synthesis; most of the synthetic approaches described herein were developed using standard, commercially available linkers (originally devised for solid-phase peptide synthesis). The type of structure prepared in a traceless fashion is not restricted. The individual synthetic approaches are divided into eight sections, each devoted to a different methodology for traceless synthesis. Each section consists of a brief outline of the synthetic strategy followed by a description of individual reported syntheses.

Thiol substrate-promoted dehydrogenative cyclization of arylmethyl thiols with ortho-substituted amines: a universal approach to heteroaromatic compounds

A thiol substrate-promoted one-pot synthesis of a library of heteroaromatic compounds was developed.

Efficient solid-phase synthesis of 3-substituted-5-oxo-5H-thiazolo[2,3-b]-quinazoline-8-carboxamides under mild conditions with two diversity positions

Highly efficient solid-phase synthesis of thiazolo[2,3,b]quinazolines under mild conditions was developed using resin-bound 2-amino-terephthalamic acid, Fmoc-NCS, and bromoketones. Primary amines immobilized to an acid-cleavable backbone amide linker were acylated with 1-methyl-2-aminoterephtalate. Following cleavage of the methyl ester, Fmoc-NCS was used to form a resin-bound thiourea. Bromoketones were subsequently added to form an aminothiazole ring and the cyclization was performed using DIC/HOBt to afford thiazolo[2,3,b]quinazolines. Highly efficient solid-phase synthesis is amenable to high throughput/combinatorial synthesis.

Intramolecular Hetero Diels−Alder (Povarov) Approach to the Synthesis of the Alkaloids Luotonin A and Camptothecin†

[reaction: see text] Pyrrolo[3,4-b]quinolines can be formed through the coupling of anilines with N-propargylic substituted heterocyclic aldehydes in the presence of mild Lewis acid catalysts (Ln(OTf)3). The coupling proceeds through sequential imine formation and a formal intramolecular aza-Diels-Alder (Povarov) reaction. This approach was applied in a total synthesis of luotonin A and a formal synthesis of camptothecin.