Structural studies of a polysachcharide from litsea glutinosa and the synthesis of some acridones and coumarins

Abstract

This thesis consists of three parts. Part-1 describes the structural studies of an arabinoxylan isolated from Litsea glutinosa {Lour)., Arabinose and the xylose were the major neutral Sugars present in the water soluble polysaccharide isolated from the mucilaginous bark of Litsea Siutinosa (Lauraceae), The molar ratio of D-xyloseL-arabinose was 1.0 : 3.5. Methylation analysis, partial hydrolysis and <formula> and <formula> spectroscopy indicated a backbone of (1-4)-linked 8-D- xylopyranosyl residues substituted at both positions 2 and 3 with side chains composed of either Single or (1-3)-linked arabino- furanosyl residues. Both a-L- and B-L- arabinofuranosyl residues were present. Side chains composed of two 8-L-arabinofuranosyl residues are probably attached at Q-2 of some xylosyl residues. Part-2 of the thesis discusses the total synthesis of twenty acridone alkaloids, eleven of which are new acridones. 1,3-Dihydroxy-9-acridone (31) was synthesisedfrom methyl anthranilate and phloroglcinol. Selective methylations of compound (31), gave 1-hydroxy-3- methoxy-10-methyl-9-acridone (32), 1,3-dimethoxy~-10- methyl-9-acridone (33) and 1,3-dihydroxy-10-methyl-9- acridone (34). The iodination of (31) afforded a new acridone, 1,3~-dihydroxy-2,4-diiodo-9-acridone (35) while compounds (32), (33) and (34) gave 1l-hydroxy-2- iodo-3-methoxy-10-methyl-9-acridone (36), 2-lodo-1,3- dimethoxy-10-methyl-9-acridone (37) and 1,3-dihydroxy- 4-iodo-10-methyl-9-acridone (38) respectively. Methylation of compound (35) gave another new acridone, 2,4-diiodo-1,3-dimethoxy-10-methyl1-9- acridone (39). The palladium catalysed Heck condensation reaction of compounds (36), (38) and (39) with 2-methyl-3-butene-2-o0l afforded three new acridone alkaloids, 1-hydroxy-2-(3-hydroxy-3-methyl-1- butenyl )-3-methoxy-10-methyl-9-acridone (40), 1,3- dimethoxy-2-(3-hydroxy-3-methyl-1-butenyl )-10-methyl- $-acridone (42) and 2,4-bis(3-hydroxy-3-methyl-1- butenyl )-1,3-dimethoxy-10-methyl-9-acridone (43) respectively, while compound (37) affoded a naturallyoccurring acridone, isonoracronycine (41), Methylation of (41) gave isoacronycine (44). Methyl-6-amino-2,3-dimethoxybenzoate (51) Which was synthesised from 6-formyl-2,3-dimethoxybenzoic acid (45), was treated with phloreglucinol to give two new acridone alkaloids, 1,3,8-trihydroxy-7-methoxy-9- acridone (52) and 1,3-dihydroxy-7,8-dimethoxy-9- acridone (53). The selective methylation of (52) and (53) gave another four new acridones, 1,8-dihydroxy- 3,7-dimethoxy-9-acridone (5 ), 1,8-dihydroxy-3,7- 5), l-hydroxy-3,7,8-dimethoxy-10-methyl-9=acridone ( trimethoxy-10-methyl-9-acridone and 1,3,7,8- tetramethoxy-10-methyl-QG-acridone (57). Part-3 of the thesis deals with the total synthesis of (F)-suberenol (3) from 4-bromoresorcinol and describes the use of (E)-suberenol as a precursor for the synthesis of related coumarin derivatives. The synthesis of three wavuval iy occurring coumarins, cyclobisuberodiene (9), dihydrosuberenol (11) and ethylsuberenol (12) and three new coumarins, (#)-suberodiene (8), (E)-suberenene (10) and methylsuberenol (13), a new coumarin dimer (14) and three new acridone-coumarin dimers (Acrimarins), 1,3- dihydroxy-2-[1-7-(methoxy-2-oxo0-2H-chromen-6-yl )-3- methyl-2-butenyl ]-10-methyl-9-acridone (15), 1- Leinony—di-methons-2-[4~7-lnathong~2<oxo~2ieohwomen=Be yl)-3-methyl-2-butenyl ]-10-methyl-9-acridone (16) and 1,3-dihydroxy-2-[1-7-{methoxy-2-o0x0-2H-chromen-6-yl )- 3-methyl-2-butenyl]-9-acridone (17) are described in this part of the thesis.