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Preparation of 2,9-dioxabicyclo[3.3.1]nonanes. A model for tirandamycin

โœ Scribed by Philip DeShong; Subban Ramesh; Joseph J. Perez; Cynthia Bodish

Publisher
Elsevier Science
Year
1982
Tongue
French
Weight
214 KB
Volume
23
Category
Article
ISSN
0040-4039

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โœฆ Synopsis

An efficient synthesis of a 2,9-dioxabicyclo[3.3.l]nonane system, similar to that of tirandamycin, is accomplished from 2,3_dimethylfuran. Tirandamycin ls2 (1) is a member of the 3-acyl tetramic acid family of antibiotics which -1,3 includes streptolydigin 4

, nocamycin , antibiotics Bu-2313 A and B5, ikarugamycin6, and others.

7-9 It displays antibiotic activity 10 , as well as inhibitory activity against DNAdirected RNA polymerase. 11 These activities contrast sharply with those of simple 3-acyl tetramic acids and it has been proposed that the altered activity results from the presence of the 2,9-dioxabicyclo[3.3.l]nonane moiety found in these systems. 1

Ireland and co-workers have reported a synthesis of tirandamycinic acid (L), a degradation product of l_', in which the bicyclic ring system was prepared from D-glucose in a multistep scheme." Recently, a second approach to the bicyclic system of tirandamycin has been reported by Ziegler and Thottathil which involves a furan precursor. 13 This latter report has prompted us to report our preliminary results on a similar system. We have found that the 2,9-dioxabicyclo [3.3.l]non-7-ene-6-one system 2 can be efficiently prepared from 2,3-dimethylfuran (3)(see Scheme).

Lithiation of 2,3-dimethylfuran (5; "BuLi, TMEDA, ether, R.T.) followed by condensation with THP ether-aldehyde 5 15,16 17 -gave furan-alcohol 5 , as a mixture of diastereomers, in 65% yield after flash chromatography. The ratio of diastereomers was approximately 27:16:15:42 based upon HPLC analysis. The diastereomers, although unstable to chromatography, could be purified by HPLC. Rather than separate the diastereomers (6) at this point however, it was advantageous to employ the mixture without purification. enone as 2 and not the epimer 4. 13C NMR (CDC13):

6

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