Actinomycins

Actinomycin.—Kynurenine and 3-hydroxykynurenine are actinomycin precursors in Streptomyces antibioticus (cf. Vol. 6, p. 42). Recently, kynureninase and hydroxykynureninase activity has been identified in S. parvulus cultures and the latter activity was found to show correlation with actinomycin formation.57 

Chloramphenicol.—A synthetase which converts chorismic acid into p-amino-phenylalanine (an intermediate in chloramphenicol biosynthesis) has been partly characterized it requires an aminotransferase and pyridoxal phosphate for activity.58 

Actinomydn.—4-Methyl-3-hydroxyanthranilic acid (131) is an important precursor for actinomycin (132) cf. ref. 6. Further support for its role as a biosynthetic intermediate is its accumulation in mutants of Streptomyces parvulus that are unable to synthesize (132).  

Troost and E. Katz, J. Gen. Microbiol, 1979, 111, 121 see also refs, cited therein. 

2-Amino-4,6-dimethyl-3-oxo-3//-phenoxazine-l,9-dicarboxylic acid also named actinocin is the chromophor of the red antineoplastic chromopeptide actinomycin D (formula A). Two cyclopenta-peptide lactone rings (amino acids L-threonine, D-valine, L-proline, sarcosine, and A-methyl-L-valine) are attached to the carboxy carbons of actinocin by two amide bonds involving the amino groups of threonine. 

The attachment of the cyclopentapeptide lactone rings to the carboxy functions at C-1 and C-9 of the actinocin heterocycle B can be deduced from the HMBC plot d Protons 1-H (Sh = 7.35) and S-H Sh = 7.62) of the heterocycle display an AB system in the proton domain. The attached carbon nuclei have been assigned by CH COSY in the literature (5///5c = 7.55/130.33 and 7.(52/125.93, ref p. 426) the other carbon atoms of the benzenoid ring within the phenoxazone are assigned as reported by correlation via Jqh and Vc// coupling detected in d which additionally shows a weak Jqh correlation signal of 8-iTwith C-5a (5///5c = 7.(52/140.53). 

Evaluation of the HH ROESY (c) verifies the amino acid sequence of the cyclopentapeptide lactone ring attached to C-9 of actinocin by means of the NOE induced spatial correlation signals labelled in the formula C. The a- and p-protons of threonine in both cyclopentapeptide lactone rings are sufficiently separated but close to each other. This applies to the other amino acid protons with the exception of TV -methylvaline, in which proton signals overlap (Table 55.1). Therefore, starting from the a- and P-protons of threonine (Sh = 4.61 and 5.15), the sequence Thr-Val-Pro-Sar-MeVal attached to C-1 of actinocin is similarly verified in the HH ROESY as shown in formula C. The connection Sar-MeVal is established by the spatial correlations between the B-protons of sarcosine and the TV -methyl-protons of A -methylvaline in both rings (Su = 4.71/2.92 and 4.78/2.89). 

Additional significant spatial correlations (NOE) in the HH ROESY experiment (c) provide information concerning the distances of some protons from one ring (at C-9) to the other (at C-1). Such closely spaced protons are  

Molecular modelling calculations using values of smaller than 3 Angstrom units for these proton-proton distances can be performed to obtain an optimized picture of the molecule. But this exceeds the scope of this book. 

The results of Table 55.1 complete the assignment of all proton shifts of both cyclopentapeptide lactones as far as possible as shown in formula D. 

52/125.93, ref. p. 426) the other carbon atoms of the benzenoid ring within the phenoxazone are assigned as reported by correlation via and Jqh coupling detected in d which additionally shows a weak Jch correlation signal of 8-//with C-5a ( 5///5c = 7.52/140.53). 

Proton %-H (Su = 7.62) gives a correlation signal via coupling in the HMBC plot d with the carboxy carbon at 6c = 166.18 which also correlates with the proton of threonine at Sh = 7.15. 

Evaluation of the HH ROESY (c) verifies the amino aeid sequenee of the eyelopentapeptide laeto-ne ring attaehed to C-9 of aetinoein by means of the NOE indueed spatial eorrelation signals la- 

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Those herbicides that block mitotic entry decrease or prevent the formation of mitotic figures in meristems. Amino acid, protein, RNA, DNA, and ATP synthesis and/or utilization can all attest cell growth (163,166). Although not registered as herbicides, cycloheximide [66-81-9] inhibits mitotic entry by inhibiting protein synthesis (167) hydroxyurea/727-(97-/7 inhibits DNA synthesis (168) and actinomycin D [50-76-0] nh2oix.s RNA synthesis (167). 

In 1939 the isolation of a mixture of microbial products named tyrotbricin from a soil bacillus was described. Further investigation showed this material to be a mixture of gramicidin and tyrocidine. In rapid succession the isolation of actinomycin (1940), streptothricin (1942), streptomycin (1943), and neomycin (1949), produced by Streptomjces were reported and in 1942 the word antibiotic was introduced. Chloramphenicol, the first of the so-called broad spectmm antibiotics having a wide range of antimicrobial activity, was discovered in 1947. Aureomycin, the first member of the commercially important tetracycline antibiotics, was discovered in 1948. 

Dactinomycin. Dactinomycin [50-76-0] (actinomycin D, actinomycin Cl, Cosmegen), is the only actinomycin in clinical use. 

Almost all actinomycins have the same chromophore, a planar phenoxa2inone dicarboxyUc acid called actinocin. In dactinomycin, the stmcture of which is shown in Figure 12, the two pendent pentapeptide lactones are identical, but in other actinomycins these lactones may be different. In other actinomycins the first amino acid, amide linked with actinocin, is usually L-threonine, as in dactinomycin the second position is sometimes D-aHo-isoleucine instead of D-valine the third position may be sarcosine or oxoproline the fourth position is sarcosine and the fifth position is sometimes /V-methyl isoleucine instead of /V-methylvaline. The lactone ring is always present. 

Fig. 12. Stmcture of dactinomycin (actinomycin D) where MeVal = N-methylvaline and Sar = sarcosine.

Total synthesis of dactinomycin has been accompHshed, and at least thirty natural actinomycins and many synthetic and semisynthetic actinomycins have been tested (220,221,228). At one time cactinomycin [8052-16-2] (actinomycin C), a mixture of actinomycins D, C2, and C3, was sold as an antineoplastic. 

U. HoUstein, Chem. Rev. 74, 625 (1974) "Sebnan A. Waksman Conference on Actinomycins Their Potential for Cancer Chemotherapy," Cancer Chemother. Rept. 58 (1974). 

Actinocin — see Phenoxazine-l,9-dicarboxylic acid, 2-amino-4,6-dimethyl-3-oxo-Actinoleutin applications, 3, 195 Actinomycins... 

The NMR experiments 55 are obtained from actinomycin D in order to check the amino acid sequence, to assign proton-proton and some carbon-proton connectivities, and to deduce informations concerning proton distances and the spatial structure of both cyclopentapeptide lactone rings. Conditions CDCI3, 10 mg per 0.3 ml, 25 °C, 500 MHz H), 125 MHz ( C). (a) HH COSY plot ... 

Aromatic macrocycles, flat hydrophobic molecules composed of fused, heterocyclic rings, such as ethidium bromide, acridine orange, and actinomycin D... 

Chemical Name Complex actinomycin, see structural formula Common Name Meractinomycin Actinomycin D Actinomycin Aj Structural Formula ... 

The final extract is faintly pale yellow in color, whereas the previous extracts are orange. The combined ether extracts are concentrated to dryness and about 3 grams of a reddish-brown residue is obtained. The residue is stirred with approximately 400 cc of petroleum ether for two to three hours, the solvent decanted and the residue treated again with approximately 400 cc of petroleum ether. A pale yellow oil constituting crude actinomycin... 

One of the key steps in the synthesis of actinomycin D (241 Scheme 3.88) and its serine analogue involved the regio- and stereoselective ring-opening of aziridine 238 with the acid 239 [138, 139]. This transformation took place in methylene... 

Hashimoto, Y., Sugawara, M., Masuko, T., and Hojo, H. (1983). Antitumor effect of actinomycin D entrapped in liposomes bearing subunits of tumor-specific monoclonal immunoglobulin M antibody. Cancer Res., 43, 5328-5334. 

Phenoxazines — The microbial phenoxazines like actinomycins are well-known antibiotics. Actinomycin D produced by Streptomyces anibioticus is an effective antineoplastic agent that inhibits nucleic acid synthesis. The main function of ommochromes is to act as screening pigments in the eyes of insects and other arthropods, as pattern pigments in the integument, and as excretion products of excess tryptophan. ... 

C62H85BrNi2Oie,2C1oH13N504-11 H20 7-BromoactinomycinDbis(2 -deoxyguanosine), undecahydrate (BRAXGU)306 P212121 Z = 4 Dx = 1.36 R = 0.094 for 4000 intensities. The co-crystals contain one actinomycin D (chromophore part, only, is shown in the... 

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