A simple and efficient procedure for the synthesis of 5-methyl-3,30-dioxo-3H,30H-spiro[furan-2,10-isobenzofuran]-
3,30-dione derivatives, proceeding via a condensation reaction between ninhydrin and various
1,3-dicarbonyl compounds followed by oxidative cleavage of the corresponding 3a,8b-dihydroxy-2-
methyl-4-oxo-4,8b-dihydro-3aH-indeno[1,2-b]furans is presented. The syntheses were carried out in
water at room temperature and proceeded with short reaction times to give the products with high
yields. The structural assignments were supported by IR, 1H NMR, 13C NMR, and mass spectrometry data.
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Spirocyclic lactones and their derivatives are widely found in
medicinal and natural product chemistry.1 The structural rigidity
imparted by spirofusion, in association with the latent functionality
of the lactone, is postulated as the source of medicinal activity.2
Like spirolactones, furan and its derivatives play an important role
in organic chemistry, due to their presence in many natural products
and pharmaceuticals and as building blocks for the synthesis
of complex natural metabolites.3 Furthermore, multi-functionalized
furans are versatile synthetic reagents for the synthesis of
various heterocyclic compounds.4 The isobenzofuran structure
exists in many natural compounds and its derivatives display various
biological activities associated with antifungal, antidepressive,
antisecretory, and antitumor function as well as having other uses
including colorants and perfumes.5a,b In addition, many of its
derivatives have been used as synthons for the synthesis of
complex molecules.5c,d As an example, 4-phenyl-3H,30H-spiro
[furan-2,10-isobenzofuran]-3,30-dione, known as fluorescamine
and containing furan and isobenzofuran motifs in its structure
(Fig. 1) is not inherently fluorescent but can react with primary
aliphatic amines to produce strongly fluorescent products. This
compound has been widely used to detect amino acids, peptides,