| सारांश: | <p>More than fifty polyacetylenic compounds produced by micro-organisms have been isolated and characterised since the discovery of the allenic polyacetylene, mycomycin, in 1952. A review of the sixteen natural allenic polyacetylenes which have been isolated and their structures elucidated, is included. this review is followed by a summary of the methods published by Brewster in 1959 for the correlation of observed optical rotations with the configurations of coat pound a having simple asymmetric centres.</p> <p>Four allenic polyacetylenes (I-IV) have been isolated from the culture medium of the fungus <em>Odontia bicolor</em>.</p> <ol type="I"> <li>HC≡C.C≡C.CH=C=CH.CH<sub>2</sub>.CH<sub>2</sub>.CH<sub>2</sub>OH</li> <li>HC≡C.C≡C.CH=C=CH.CH<sub>2</sub>.CH<sub>2</sub>.CH<sub>2</sub>.CH<sub>2</sub>OH</li> <li>HC≡C.C≡C.CH=C=CH.CH(OH).CH<sub>2</sub>.CH<sub>2</sub>OH</li> <li>HC≡C.C≡C.CH=C=CH.CH(OH).CH<sub>2</sub>.CH<sub>2</sub>.CH<sub>2</sub>OH</li> </ol> <p>In addition, substantial evidence has been presented for assigning the structure (V) to a non-allenic polyacetylene which is also produced by the fungus.</p> <ol start="5" type="I"> <li>HC≡C.C≡C.CH=CH.CH=CH.CH<sub>2</sub>.CH<sub>2</sub>.CH<sub>2</sub>OH</li> </ol> <p>The allenic metabolites isomerised readily in dilute alkali to fora triynes since the allene group in each case is conjugated to a diacetylene unit. The triynes formed from the diols had a terminal ethynyl group, whereas those formed from the alcohols had no terminal ethynyl group. The isomerised C<sub>10</sub> alcohol (I) was shown to be identical to synthetical specimen with the structure (VI). The mechanisms of these isomerisations are discussed.</p> <ol start="6" type="I"> <li>CH<sub>3</sub>.C≡C.C≡C.C≡C.CH<sub>2</sub>.CH<sub>2</sub>.CH<sub>2</sub>OH</li> </ol> <p>An isopropylidene derivative of the C<sub>10</sub> 1,3-diol (III) was prepared and fully characterised. The absolute configuration of the C<sub>3</sub> secondary alcohol centre in this diol was deduced to be (S) from a consideration of observed optical rotations and the use of Brewster's methods. Certain characteristics of the infrared spectra of the diols and the 1,3-isopropylidene derivatives have been noted.</p> <p>Two polyacetylenes have been isolated from the culture medium of the fungus <em>Clitocybe rhizophora</em> and shown to have the structures (VII-VIII).</p> <ol start="7" type="I"> <li>HOCH<sub>2</sub>.CH(OH).C≡C.C≡C.CH(OH).CH<sub>2</sub>.CH<sub>3</sub> <li>HOCH<sub>2</sub>.CH(OH).C≡C.C≡C.CO.CH<sub>2</sub>.CH<sub>3</sub> </li></li></ol> <p>They are unique among the polyacetylenes so far isolated from micro-organisms in being the first diacetylene and the first ketone to be isolated. The structural determination for the diyne-triol (VII) was confirmed by investigating the nuclear magnetic resonance spectrum of its isopropylidene derivative and of the products of hydrogenation and of sodium borohydride reduction of this derivative.</p> <p>The absolute configurations of the secondary alcohol centres at C<sub>2</sub> in both the natural compounds and at C<sub>7</sub> in the triol were deduced to be (S) from observed optical rotations and the use of the methods of Brewster. Certain characteristic in the infrared spectra of the 1,2-isopropylidene derivative were noted and compared with the data from the 1,3-isopropylidene derivatives of the allenic C<sub>10</sub> 1,3-diol (III) from <em>Odontia bicolor</em>.</p> <p>The synthesis of a polyacetylenic diacid (IX) from <em>Merulius lachrymans</em> has been described in an appendix.</p> <ol start="9" type="I"> <li>HOOC.C≡C.C≡C.C≡C.CH<sub>2</sub>.CH<sub>2</sub>.COOH</li></ol>
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