Cordycepin structure

The nucleoside cordycepin was isolated from cultures of Corofy- ceps militaris and found to be 3 deoxyadenosine Write its structural formula j... 

It is not unlikely that more antibiotic substances having nucleoside structures will be found in Nature. Already, just in the realm of the purine nucleosides, three antibiotic substances, nebularine,7,176 cordycepin,6 and puromycin8,173 have been isolated from natural sources. 

The mold Cordyceps militaris Linn, contains an antibiotic substance, cordycepin (15) which, on acid hydrolysis, gives adenine and a deoxyaldo-pentose that was named cordycepose. The ultraviolet spectrum of the nucleoside indicates that the sugar is attached to the 9-position of adenine, but the complete structure of the su moiety of cordycepin has not been elucidated. 

Bentley HR, Cunningham KG, Spring FS. Cordycepin, a metabolic product from cultures of Cordyceps militaris (Linn.) Link. Part II. The structure of cordycepin. J Chem Soc 2301-2305, 1951. 

A series of phospholipid conjugates of general structure (13) and (14) of AZT and 3 -deoxyadenosine (cordycepin) have been synthesised from the corresponding phosphoramidites (15) and (16). It is envisaged that they will act as prodrugs of the parent nucleoside monophosphates which possess enhanced membrane permeability. 

Cordycepin (3 -deoxyadenosine) is a compound that can block the synthesis of RNA, because a cordycepin residue in an RNA chain lacks the 3 -OH end needed for chain extension by RNA polymerase. The structure of cordycepin is shown below. 

Fig. 1. Nueleoside antibioties. Structures of cordycepin, psicofuranin, decoyinin and angustmycin A.

Cordycepin was one of the first adenine-nucleoside analogs isolated from growing cultures of fungi (Cunningham et al., 1951). This nucleoside is produced by Cordyceps militaris, Bentley et al. (1951) reported cordycepin as an adenine-sugar nucleoside (I). Their structural elucidation of the sugar moiety, cordy-... 

Ribose was assimilated from the culture medium very rapidly, but it failed to contribute a measurable quantity of radioactivity in the isolated cordycepin. Acetate-1and isovalerate-l- C were also used. These studies were based on the assumption that the structure of the sugar was a branch chain pentose. As expected, neither acetate nor the isovalerate were incorporated into 3-deoxyribose. More recently, Suhadolnik et al. (1964b) have shown that adenosine or a phos-phorylated adenosine is the direct precursor for cordycepin. These results were obtained by adding adenosine-U- C to a growing culture of C. militaris. The percent distribution of the carbon-14 in the adenine ribose of the adenosine added to the fermentation medium was 40 60. The distribution of the carbon-14 in the adenine 3-deoxyribose of the cordycepin isolated from two separate experiments... 

Suhadolnik, R. J., and J. G. Cory Further evidence for the biosynthesis of cordycepin and proof of the structure of 3-deoxyribose. Biochim. et Biophys. Acta 91, 661 (1964 a). 

Hanessian et al. (1966) have supplied additional proof for the structure of cordycepin as 3 -deoxyadenosine by the technique of mass spectrometry. Their mass spectral data were consistent with the earlier reports by Kaczka et al. (1964b) and SuHADOLNiK and Cory (1964a) that cordycepin is indeed 3 -deoxy-adenosine. 

U- C is the direct precursor. Cordycepin-U- H is not a direct precursor for 3 -amino-3 -deoxyadenosine. Therefore, adenosine or its 5 -phosphate is the precursor for 3 -deoxyadenosine and 3 -amino-3 -deoxyadenosine. Since these two nucleosides are structurally related, it may be that adenosine is converted to a compound that is a common precursor. 

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