Dehydro-a-lapachone

Although it presents diverse stereogenic centers, the authors do not indicate if this compound was found as a racemic mixture. Dehydro-a-lapachone (58) and dehydro-p-lapachone (59) are formed by oxidative cyclisation of lapachol with DDQ [134-135]. The reduction of quinones to hydroquinones is a quick, quantitative, and reversible process, which is common both to ortho and para quinones [136]. The transformation of lapachol to p-lapachone in acid media was treated previously in section-2. 

There are also natural products of the 3,4-dehydro series (314). 3-Methyl-314 was isolated from heartwood of Paratecoma peroba (68N38), and the 2,2-dimethyl derivative (310, R = H) from wood of Rademachera sinica (81JCS(P1)2764). The last compound (dehydro-a-lapachone) was obtained also from isolapachol and DDQ 311 is formed first and then isomerized to 310 in the presence of acid (62MI1 69JOC120 78CJC517). 

A series of nine naphtho[2,3-h]furan-4,9-diones (e.g., lapachol, dehydro-ot-lapachon, efliyl- and isopropylnaphtho[2,3-f>]fiiran-4,9-dione) were extracted from bark and well resolved on a Cjg column (A = 254nm and 280nm) using a 20-min 25/20/55 45/25/40 acetonitrile/methanol/water (0.1% H3PO4) gradient [1253]. 

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