V. Kamat, R. Asolkar, J. K. Kirtany
Apr 9, 2013
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ChemInform
Abstract
Lactarochromal 1, a metabolite of the fungus Lactarius deliciosus, was isolated by Ayer and Trifonov 1 , and characterized on the basis of spectroscopic data. Since structure 1 was based only on spectral data, a synthetic support 2 was provided to confirm the assigned structure by its facile synthesis utilising 2,2,6-trimethylchroman-4-one 2 as the key intermediate. However, the K2S2O8-Cu (II) mediated oxidation 3 of the aromatic methyl group in 2 produced appreciable amount of the corresponding acid at the cost of desired product 1. To circumvent this problem, it was preferred to introduce the formyl group directly on preformed chromanone skeleton at the last stage of synthesis. In accordance with this protocol, herein is reported an efficient and simple synthesis of 1 starting from 6-amino-2,2-dimethylchroman-4-one 3 (Scheme I). The starting material 3 for the synthesis of 1 was prepared, in the present case, starting from paracetamol via the known intermediates: 4′acetoxyacetanilide 4 , 2′-hydroxy-5-acetamidoacetophenone 5 and 6-acetamido-2,2-dimethylchroman-4-one 6 . The amino group of 3 was diazotized and the resulting diazonium salt was treated with aqueous KI to furnish the corresponding iodochroman-4-one 4, hitherto unknown. The iodo compound 4 has been fully characterized by spectral data (see experimental section). Finally, the formyl group was introduced smoothly on the chromanone moiety by treating the lithium salt of 4 with N-formylpiperidine to furnish lactarochromal 1 as a crystalline solid in 93% yield. The melting point and spectral data (IR, 1 H and 13 C NMR and MS) of the synthetic 1 were in good agreement with the published 1,2 data.