N. V. Subba Rao

Synthesis of naturally occurring partial methyl ethers of myricetin

The synthesis of combretol, annulatin, and europetin—naturally occurring partial methyl ethers of myricetin—is described. Condensation of 2, 4, 6-trihydroxy-ω-methoxyacetophenone with tri-O-methyl galloyl chloride or tri-O-benzyl galloyl chloride furnished the appropriate 3-methoxyflavones, which by a series of reactions furnished the natural myricetin derivatives.

Strength of chelation in benzoins

The infrared and ultraviolet absorption spectra of substituted benzoins have been studied with a view to find the influence of ring substituents on the strength of chelation in benzoins. The strength of chelation was found to be in the order 4-dimethylamino benzofuroin > 4-dimethylamino benzoin > 4-methoxy benzoin = anisoin > benzoin = furoin.

A new route to the synthesis of coumestans

2-Chlorocyclohexanone ~ was refluxed with 4-hydroxy coumarin in molar proportions in boiling xylene using anhydrous potassium carbonate a s a basic condensing agent for four hou.rs. At the end of the reaction, the xylene solution was decanted and concentrated to a small bulk when a white solid separated. The crude product was filtered and repeatedly digestea with aqueous sodium bicarbonate solution. The bicarbonate insolubles were then washed with dilate hydrochloric acid and finally with water, free from lhe acid.. The crude product thus obtained was recryst2Alised from methanol, when a colourless crystalline substance with a m.p. 173 ~ C, different from starting material, was obtained. Elemental analysis indicated the absence of halogen and the compound aceounted for C15 skeleton. The I.R.. speetrum of the compound dial not reve,,l the presence of hydroxyl and showed ah absolption around 1710 cm -1 assignable to lactone carbonyl. This indicated that the hydroxyl i n 4-hydroxy-coumarin and halogen of 2-chlorocyclohexanone were involved in the condensation, in which case the resulting product must have been an ether with the carbonyl of the cyclohexyl moiety free. The compoand however did not reveal the presence of ah additional carbonyl either in I.R. of by the qualitative tests. Further, in the N.M.R. of the compound, there was no indication for the presente of a ffee proton in 3-position of .coumarin and therefore suggested that 3 and 4-positions of coumarin are involved in the condensation wittt 2-chlorocyclohexanone forming a fused 5-membered ring. From an analogy of the condensation of 2-chlorocyclohexanone with fl-naphthol reported by Osdene attd R~seP, it appeaxed probable to suppose that the reaction proceeded through ah intermediate 3-(2-oxo-cyclohexyl)-4-hy 91 coumarin (I)