3-Peltatin methyl ether

The methyl ether (23) was compared with analogous known lignans. The H-NMR spectra of compound (2 3) differed from that of dehydro- / -peltatin methyl ether (24) which has the methoxy group at the C-8 position (ref. 25) and from that of dehydrohernandin (25) which has the methoxy group at the C-5 position (ref. 

From the above facts, compound (15) was presumed to be tetrahydronaphtha-lene-type lignan with a trimethoxyphenyl group, a methoxy group and a methyle-nedioxy group. A known lignan with the same molecular formula and functional groups was reported as / -peltatin A methyl ether (3 6 ) (ref. 37), mp 162 — 163 C,... 

On the other hand, the crystal structures of 5 -demethoxy- / -peltatin A methyl ether and 2 -bromopodophyllotoxin were clarified by X-ray analyses (ref. 43) and it was established that the configuration of these lignans were 2- a -H, 3- / -H and 4- a -aryl. In view of the above experimental results and the conclusions obtained from X-ray analyses of analogous lignans, the structure of hernandin is presumed to be 5-methoxydesoxypodophyllotoxin (15). To confirm this, the absolute configuration of compound (15) was determined by X-ray analysis. 

In section 6.2, the synthesis of ( )-hernandin which has 2,3-trans, 3,4-cis configuration, was described. This method was adopted for the syntheses of analogous 4-phenyltetralin-type lignans and we succeeded in synthesizing ( )-de-soxypodophyllotoxin (3) and ( )- / -peltatin A methyl ether (3 6). The syntheses were carried out through the scheme in Chart 17. 

Syntheses of / -Peltatin A and B Methyl Ether from Desoxypodophyllotoxin (ref. 70)... 

We were interested in the syntheses of related 4-aryltetralin-type lignans by utilizing desoxypodophyllotoxin (3), which is available in large quantities from the plant seeds. The synthetic route to / -peltatin A methyl ether (36) and B methyl ether (83) (ref. 37) from desoxypodophyllotoxin (3) is shown in Chart 18. 

The structure of compound (81) as 8-bromodesoxypicropodophyllin had not been proved at this stage, but was clarified by the fact that compound (81) was converted to compound (8 2) on treatment with basic reagents, as described later. Subsequently, several methods were examined to convert compound (81) into / -peltatin A methyl ether (3 6) and B methyl ether (8 3) by direct substitution of the bromine with a hydroxy group and methoxy group. Attempts to convert compound... 

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