5. ANTIBIOSIS AND ANTIBIOTICS
267
Cordyceps militaris; the sulfamic ester of an unidentified hexose
(Ο 6 Η 10 Ο 5 —OS0 2 NH 2 ) in nucleocidin from Streptomyces calvus. The
common pentose D-ribose is linked to purine in nebularin, which is produced by Agaricus nebularis and several strains of streptomycetes, and
to 4-aminopyrrolo-(2,3-cZ)-pyrimidine in the closely related streptomycete
antibiotics tubercidin (XIII), toyocamycin (54a) from S. albus and
S. toyocaensis, unamycin Β from S. fungicidicus, monilin from S. sakaensis, and vengicide from S. vendargensis. In puromycin (XIV), from
S. alboniger, 3-amino-3-deoxy-/?-D-ribose is linked to 6-dimethylaminopurine (54b) and to O-methyl-L-tyrosine. This antiprotozoal and anticancer antibiotic is known to block a late stage of protein synthesis
(55a-55e),
possibly by competing with RNA-aminoacyl complexes and
OH
OH
OH
CH 2
OH
Angustose
D-Psicose
Cordycepose
(Χ)
(XI)
(XU)
H 3 C CHg
O-methyltyrosine
Tuberc idin
a
Puromyc in
(ΧΠΙ)
(XIV)
° In the related toyocamycin, there is an additional CN group in position 5.