8-Hydroxy-3,4-dihydroisocoumarin

Scheme 13. Conversion of ( )-3-benzyl-7-methoxyphthalidesto ([ )-3-aryl-8-hydroxy-3,4-dihydroisocoumarin...

The xenocoumacins exhibit UV spectra in neutral and al)solutions similar to that of mellein (ref.12) and characteristic of the 8-hydroxy-3,4-dihydroisocoumarin chromophore. The Xmax (MeOH) occurs at 247 and 314 nm. Upon addition of alkali there is a bathochromic shift from 314 to 347 nm. Similar UV spectra were also reported for the amicoumacins (ref.101), baciphelacin (ref.102) and all the AI-77 compounds except AI-77-G (ref. 99). With AI-77-G (33), the dihydroisocoumarin ring has been hydrolysed causing a shift in Xmax (MeOH) to 298 nm. The 8-hydroxy-3,4-dihydroisocoumarin ring system also exhibits a characteristic fluorescence spectrum. 

Condon, P., J. Kuc., and H.N. Draudt Production of 3-Methyl-6-methoxy-8-hydroxy-3,4-dihydroisocoumarin by Carrot Root Tissue. Phytopathology 53, 1244 (1963). 

DC037 Sarkar, S. K., and Phan Chon Ton. Biosynthesis of 6-hdroxy-8-methoxy-3-methyl-3,4-dihydroisocoumarin and 5-hydroxy-7-methoxy-2-methylchromone in carrot root tissues... 

The synthesis of phthalides and dihydroisocoumarins however, has drawn much attention [424-427]. A novel AlCb-catalyzed conversion of ( )-3-benzyl-7-methoxyphthalides to ( )-3-aryl-8-hydroxy-3,4-dihydro-isocou-marin and related compounds in a single step has been elaborated (Scheme 13) [427]. Chemical transformation from dihydroisocoumarin into benzylidene-phthalide has also been realized [122]. 

An alternate synthesis from chloroindanone is also known. The key intermediate here is 5-chloro-8-hydroxy-3-methyl-3,4-dihydroisocoumarin 38 The key inter-... 

Hydroxy-l-methoxyallenyl-4,4-dialkylisochromans, available from dihydroiso-coumarins, undergo a Pd(0)-catalysed ring expansion to benzoxepanones. In the absence of the Pd catalyst, the dihydroisocoumarins can be converted direetly into a benzoxocanone (Scheme 20) <04SL481>. 

A stereospecific synthesis of both enantiomers of 8-hydroxy-3-methyl-3,4-dihydroisocoumarin, mellein, from propylene oxide has been described <97TA2153>. 

Novel tra s-3-acetyl-4-hydroxy-3,4-dihydroisocoumarins occurs through an organocatalytic intramolecular tra s-selective 6-eno/exo-exo-trig aldol reaction of 2-oxopropyl 2-formyl benzoate derivatives in good yields with high diastereo- and enantioselectivity (13S1708). 

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