Nucleoside, antibiotics phosphorylases

Showdomycin. Showdomycin (2-p-D-ribofuranosyhnaleimide) (7) is a maleimide C-nucleoside antibiotic synthesi2ed by S. showdoensis-, isoshowdomycin (8) and maleimycin (9) have also been isolated (1—6). Showdomycin is not phosphorylated by nucleoside kinase and is not a substrate for nucleoside phosphorylase. Once (7) enters the cell, it blocks the uptake of glucose and other nutrients. 

Purine-9-ylalkyl derivatives (15) containing both the phosphonic and phosphinic substituent inhibit purine nucleoside phosphorylase. Compound 15 [R = NH2, R = OH, R r4 = h, = N, X = H, X = CH2)3] had K, = 0.0026 pmol (ref. 39). The phosphonate monoesters 16 (R = Me, R = o-, m- or P-NO2) inhibit the class A j5-lactamase, probably by phosphorylation of the active site of this enzyme" . When R = Ph they also inhibit class C j5-lactamase of Enterobacter cloacae P99 and may led to new antibiotics. They should be useful as active titrants of the enzyme ... 

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