Furan ring 2,5-dihydro- from

Efforts have been focused on the synthesis of 5-ethyl-5,8-dihydro-8-oxofuro[3,2-Z)][l,8]naph-thyridine 7-carboxylic acid (37), known as DJ-6783, due to its wide spectrum of potent antimicrobial activity <86MI 837-01 >. A few synthetic routes have been studied, which were all based on the strategy of constructing the furan ring from naphthyridine derivatives. A synthetic route demonstrated in... 

The synthesis of furan fatty esters containing a phenyl substituent at the 3- or 4-position of the furan ring was reported these involved methyl 9,10-epoxy-12-oxostearate as a key intermediate (85). The mono-, di-, and triacylglycerols of a Cj g furan fatty acid were prepared by chemical and enzymatic means (86). Furanoacety-lene phytoalexins (wyerone [19] and dihydro-wyerone [20]) were prepared in multigram quantities from furfural (87). The synthesis route of compound [19] is presented in Scheme 6. 

Furan, 2,5-dialkoxy-2-( 1 -hydroxyalkyl)-2,5-dihydro-ring expansion, 1, 425 Furan, 2,5-dialkoxytetrahydro-pyrrole synthesis from, 4, 330 Furan, 2,4-dialkyl-synthesis, 4, 661, 685 Furan, 2,5-dialkyl-... 

While the synthesis of benzofuran derivatives from suitable furan derivatives has been comparatively little investigated, the synthesis of fused two-ring and three-ring compounds containing a pyridine nucleus from furan derivatives has been more successful furo[3,2-c]pyridines (345),752>753 2,3-dihydrofuro[2,3-a ]quinolines (from 4,5-dihydro-3-furoic acid),754 acrophyllin (346), and 7-hydroxydictamnine (347) (from ethyl 2-ethoxy-4-oxo-4,5-dihydrofuran-3-carboxylate),755 are examples of compounds in this class which have been prepared. 

Two other xanthones, have been isolated from the same species of Hypericum [72] a) 2-deprenylrheediaxanthone B (1,5,6 - trihydroxy-4 ,5 -dihydro - 4 , 4 , 5 - trimethylfurano - ( 2 , 3 3, 4 ) xanthone) and b) isojacareubin (1,5,6 - rihydroxy - 6 ,6 -dimethylpyrano - (2 3 3,4) -xanthone). They were peculiar in their structure, being conjugated with a furan and a pyran ring, respectively. 

The presence of five-membered rings such as cyclopentanes, cyclopentenes, and dihydro-furans in a wide range of target molecules has led to a variety of methods for their preparation. One of the most successful of these is the use of trimethylenemethane [3 -1- 2] cycloaddition, catalysed by palladiumfO) complexes. The trimethylenemethane unit in these reactions is derived from 2-[(trimethylsilyl)methyl]-2-propen-l-yl acetate, which is at the same time an allyl silane and an allylic acetate. This makes it both a weak nucleophile and an electrophile in the presence of palladiumfO). Formation of the palladium c-allyl complex is followed by removal of the trimethylsilyl group by nucleophilic attack of the... 

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