4-Deoxy-y-rhodomycinone

In studies towards the synthesis of 4-deoxy-y-rhodomycinone (114a), the steric course of the cyclization of aldehyde 110 was reexamined [118]. Aldehyde 110 was obtained as before, via condensation of aldehyde 109 with leu-coquinizarine (86) [116] (Scheme 22). Reaction of 110 with tin tetrachloride gave tetralin 111, with the (R) configuration at C-10, as the major product (epimeric ratio 5 1). The observed stereoselectivity was attributed to the prevalence of the complex (Fig. 11) with the Lewis acid chelated by the... 

Conversion of 112 into hemiketal 113 and its regioisomer, by known procedures [23,120[, followed by annelation of the mixtme with the anion of 3-cyano-l(3H)-isobenzofuranone (115) and then deprotection of the pheno-Uc hydroxy groups, fmnished O-methyl-4-deoxy-Y-rhodomycinone (114b) in 11% overall yield. Cleavage of the 0-methyl group was not achieved. 

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