Large-scale synthesis of hematoregulatory nonapeptide SK&F 107647 by fragment coupling.

Linear and convergent routes for the large-scale preparation of the hematoregulatory nonapeptide (Glp-Glu-Asp)2-DAS-(Lys)2 (2, SK&F 107647) were investigated. A convergent approach ('3 + 2'-route employing Boc-and benzyl ester protecting groups) was selected for the preparation of multihundred-gram quantities of 2. Key steps were the preparation and the coupling of tripeptide hydrochloride (HCl.H)2-DAS-(Lys(Z)-OBn)2 (6, DAS-2,7-L,L-diaminosuberic acid) and tripeptide Glp-Glu(OBn)-Asp(OBn)-OH (26). Several coupling reagents were investigated in order to reduce the amount of epimerization of this fragment coupling. TDBTU [O-(3,4-dihydro-4-oxo-1,2,3-benzotriazin-3-yl-1,1,3,3-tetrameth yluronium tetrafluoroborate] was identified as the condensation reagent of choice. Using this synthetic route > 97% pure final product in an overall yield of 35% calculated on di-Boc protected 2,7-L,L-diaminosuberic acid was prepared.

Carbocyclic 5-iodo-2'-deoxyuridine (C-IDU) and carbocyclic (E)-5-(2-bromovinyl)-2'-deoxyuridine (C-BVDU) as unique examples of chiral molecules where the two enantiomeric forms are biologically active: interaction of the (+)- and (-)-enantiomers of C-IDU and C-BVDU with the thymidine kinase of herpes simplex virus type 1.

The (+)- and (-)-enantiomers of the carbocyclic analogues of (E)-5-(2-bromovinyl)-2'-deoxyuridine (C-BVDU) and 5-iodo-2'-deoxyuridine (C-IDU) were synthesized by separate routes. Both the (+)- and (-)-enantiomers of C-BVDU and C-IDU were markedly inhibitory to herpes simplex virus type 1 (HSV-1) replication. (+)-C-BVDU and (+)-C-IDU were as inhibitory to HSV-1 as the racemic (+/-)-C-BVDU and (+/-)-C-IDU, respectively, whereas the (-)-enantiomers were only 10-fold less active. Also, the (+)- and (-)-enantiomers of C-BVDU were equally inhibitory to the growth of murine mammary carcinoma cells transformed by the HSV-1 or HSV-2 thymidine kinase (TK) gene (designated FM3A TK-/HSV-1 TK+ and FM3A TK-/HSV-2 TK+). The (+)- and (-)-enantiomers of C-BVDU and the (+)- and (-)-enantiomers of C-IDU had a remarkably similar affinity for HSV-1 TK [Ki, 0.09 and 0.19 microM for (+)-C-BVDU and (+)-C-IDU and 0.16 and 0.19 microM for (-)-C-BVDU and (-)-C-IDU, respectively]. The inhibition of HSV-1 TK by BVDU, IDU, (+)-C-BVDU, and (+)-C-IDU was purely competitive with regard to the natural substrate (thymidine), whereas (-)-C-BVDU, (-)-C-IDU, (+/-)-C-BVDU, and (+/-)C-IDU showed a linear mixed-type inhibition of HSV-1 TK. C-BVDU and C-IDU are examples of chiral molecules of which both isomeric forms are markedly active at both the cellular and enzymatic level.

Synthesis and biological activity of novel carbocyclic nucleosides.

The syntheses of several novel carbocyclic nucleosides which incorporate the cyclopentene moiety of neplanocin A will be presented. These include modified pyrimidine derivatives of the very potent antitumor agent cyclopentenyl cytosine and carbocyclic analogues of the ketohexose nucleosides psicofuranine and psicofuranosyl cytosine.

Synthesis and antiviral activity of the enantiomeric forms of carba-5-iodo-2'-deoxyuridine and carba-(E)-5-(2-bromovinyl)-2'-deoxyuridine.

Both enantiomers of the carbocyclic analogues of 5-iodo-2'-deoxyuridine (14 and ent-14) and of (E)-5-(2-bromo-vinyl)-2'-deoxyuridine (16 and ent-16) were synthesized by using (+)- or (-)-endo-norborn-5-en-2-yl acetate or butyrate, respectively, as starting materials. Against herpes simplex virus type 1 (+)-C-BVDU (16) was only slightly less active than BVDU itself, whereas (-)-C-BVDU (ent-16) proved to be 10-400-fold less effective, depending on the strain investigated. Against HSV-2 both (+)- and (-)-C-BVDU as well as (+)- and (-)-C-IDU showed minor activity. All carbocyclic analogues were inactive against TK-HSV-1 strains, pointing to the prerequisite of phosphorylation (activation) by the viral thymidine kinase (TK).

Enantiospecific synthesis of carbocyclic (+)-(E)-5-(2-bromovinyl)-2'-deoxyuridine.

(+)-1-[(1R, 3S, 4R)-3-hydroxy-4-hydroxymethylcyclopentyl]-5-[(E)-2- bromovinyl]-1H,3H-pyrimidin-2,4-dione 10 was synthesized starting from (+)-endo-5-norbornen-2-yl acetate. This chiral educt was obtained by enzymatic hydrolysis of racemic esters of endo-5-norbornen-2-ol.

5-(Haloalkyl)-2'-deoxyuridines: a novel type of potent antiviral nucleoside analogue.

Syntheses of 5-(2-haloethyl)-2'-deoxyuridines, 5-(3-chloropropyl)-2'-deoxyuridines, and 5-(2-chloroethyl)-2'-deoxycytidine are described. The antiviral activities of these compounds were determined in cell culture against herpes simplex virus types 1 and 2. All compounds were shown to possess significant and selective antiviral activity. The most potent derivative, 5-(2-chloroethyl)-2'-deoxyuridine (CEDU), inhibited HSV-1 at concentrations below 0.1 microgram/mL. It exerted measurable inhibitory effects on cell proliferation only at concentrations higher than 100 micrograms/mL. In vivo CEDU reduced the mortality rate of HSV-1-infected mice at concentrations lower than 5 mg/kg per day when given intraperitoneally and orally. Thus, it proved to be more effective in this in vivo model than the reference compounds (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) and 9-[(2-hydroxyethoxy)methyl]guanine (ACV).