19-nor-10-azasteroids, a new class of steroid 5 alpha-reductase inhibitors. 2. X-ray structure, molecular modeling, conformational analysis of 19-nor-10-azasteroids and comparison with 4-azasteroids and 6-azasteroids.

19-Nor-10-azasteroids are a new class of 5 alpha-reductase inhibitors whose activity depends on the presence of the bridgehead N-10 atom conjugated with the 4-en-3-one moiety in the A ring. The X-ray structure of 19-nor-10-azasteroid 1 has been determined and it is compared with the X-ray structure of testosterone. A complete conformational analysis of these compounds has been performed, determining the number and energy of the possible conformers, as well as the molecular flexibility of the 10-azasteroidal skeleton. Thus, MM2* molecular mechanics calculations and AM1 semiempirical energy refinements revealed that 19-nor-10-azasteroids 1-3 have four possible conformations with very small energy differences and that they are very flexible molecules. The conformational analysis has been extended to testosterone (4), which also showed conformational flexibility, with three different conformations, and to 6-azasteroid 5 and 4-azasteroid 6, for which only two thermally accessible conformations have been found. Compared to 19-nor-10-azasteroids 1-3, azasteroids 5 and 6 appear to be more rigid structures. By a best fit analysis of all conformers of 1-5 with the global minimum of testosterone (4-I) it has been found that the lowest energy conformers of 1, 3, and 5 are very close to the structure of 4-I, and among the conformers of 2, the best similarity has been observed for the highest energy conformer 2-IV.

Benzo[c]quinolizin-3-ones: a novel class of potent and selective nonsteroidal inhibitors of human steroid 5alpha-reductase 1.

The synthesis and biological evaluation of a series of novel, selective inhibitors of isoenzyme 1 of human 5alpha-reductase (5alphaR) (EC 1.3.99.5) are reported. The inhibitors are 4aH- (19-29) or 1H-tetrahydrobenzo[c]quinolizin-3-ones (35-47) bearing at positions 1, 4, 5, and 6 a methyl group and at position 8 a hydrogen, methyl group, or chlorine atom. All these compounds were tested toward 5alphaR-1 and 5alphaR-2 expressed in CHO cells (CHO 1827 and CHO 1829, respectively) resulting in selective inhibitors of the type 1 isoenzyme, with inhibitory potencies (IC(50)) ranging from 7.6 to 9100 nM. The inhibitors of the 4aH-series, having a double bond at position 1,2, were generally less active than the corresponding inhibitors of the 1H-series having the double bond at position 4,4a on the A ring. The presence of a methyl group at position 4 (as in compounds 39-40 and 45-47), associated with a substituent at position 8, determined the highest inhibition potency (IC(50) from 7.6 to 20 nM). Compounds 39 and 40, having K(i) values of 5.8+/-1.8 and 2.7+/-0.6 nM, respectively, toward 5alphaR-1 expressed in CHO cells, were also tested toward native 5alphaR-1 in human scalp and 5alphaR-2 in human prostate homogenates, in comparison with finasteride and the known 5alphaR-1-selective inhibitor LY191704, and their mechanism of inhibition was determined. They both inhibited the enzyme through a reversible competitive mechanism and again were selective inhibitors of 5alphaR-1 with IC(50) values of 41 nM. These specific features make these inhibitors suitable candidates for further development as drugs in the treatment of DHT-dependent disorders such as acne and androgenic alopecia in men and hirsutism in women.

19-nor-10-azasteroids: a novel class of inhibitors for human steroid 5alpha-reductases 1 and 2.

Steroid 5alpha-reductase is a system of two isozymes (5alphaR-1 and 5alphaR-2) which catalyzes the NADPH-dependent reduction of testosterone to dihydrotestosterone in many androgen sensitive tissues and which is related to several human endocrine diseases such as benign prostatic hyperplasia (BPH), prostatic cancer, acne, alopecia, pattern baldness in men and hirsutism in women. The discovery of new potent and selective 5alphaR inhibitors is thus of great interest for pharmaceutical treatment of these diseases. The synthesis of a novel class of inhibitors for human 5alphaR-1 and 5alphaR-2, having the 19-nor-10-azasteroid skeleton, is described. The inhibitory potency of the 19-nor-10-azasteroids was determined in homogenates of human hypertrophic prostates toward 5alphaR-2 and in DU-145 human prostatic adenocarcinoma cells toward 5alphaR-1, in comparison with finasteride (IC50 = 3 nM for 5alphaR-2 and approximately 42 nM for 5alphaR-1), a drug which is currently used for BPH treatment. The inhibition potency was dependent on the type of substituent at position 17 and on the presence and position of the unsaturation in the A and C rings. delta9(11)-19-Nor-10-azaandrost-4-ene-3,17-dione (or 10-azaestra-4,9(11)-diene-3,17-dione) (4a) and 19-nor-10-azaandrost-4-ene-3,17-dione (5) were weak inhibitors of 5alphaR-2 (IC50 = 4.6 and 4.4 microM, respectively) but more potent inhibitors of 5alphaR-1 (IC50 = 263 and 299 nM, respectively), whereas 19-nor-10-aza-5alpha-androstane-3,17-dione (7) was inactive for both the isoenzymes. The best result was achieved with the 9:1 mixture of delta9(11)- and delta8(9)-17beta-(N-tert-butylcarbamoyl)-19-nor-10-aza-4- androsten-3-one (10a,b) which was a good inhibitor of 5alphaR-1 and 5alphaR-2 (IC50 = 127 and 122 nM, respectively), with a potency very close to that of finasteride. The results of ab initio calculations suggest that the inhibition potency of 19-nor-10-azasteroids could be directly related to the nucleophilicity of the carbonyl group in the 3-position.

Design and synthesis of a new bicyclic dipeptide isostere.

The synthesis of a new Gly-Pro turn mimetic and the computational study of its ability to induce beta-turn is reported.

Effects of taurine and some structurally related analogues on the central mechanism of thermoregulation: a structure-activity relationship study.

There is large body of evidences on the role of taurine in the central mechanisms of thermoregulation in mammals, but it is not clear, whether the hypothermic effect of taurine depends on its interaction with GABA receptors or with a specific receptor. In order to answer this question, we have performed a structure-activity relationship study by using both in vitro and in vivo preparations. MicroM amounts of taurine or each of 20 analogues were injected intracerebroventricularly in conscious, restrained rabbits while rectal temperature was recorded. Receptor-binding studies, with synaptic membrane preparations from rabbit brain were used to determine the affinities of these compounds for GABA(A) and GABA(B) receptors. Furthermore, the interaction with presynaptic GABA and taurine uptake systems was studied using crude synaptosomal preparations from rabbit brain. Among the compounds tested, (+/-)-cis-2-aminocyclohexanesulfonic acid, induced hypothermia, but did not interact with GABA(A) and GABA(B) receptors neither did it affect GABA and taurine uptake, thus suggesting that its effect on body temperature is not mediated by the central GABAergic system. Interestingly, the trans-isomer was devoid of effects either in vivo or in vitro. In order to explain (+/-)-cis-2-aminocyclohexanesulfonic acid-induced hypothermia, a stereoscopic model was produced showing its possible interactions with a putative taurine brain receptor.

Synthesis of taurine analogues from alkenes: preparation of 2-aminocycloalkanesulfonic acids.

(+/-)trans 2-Aminocyclohexanesulfonic acid and (+/-)trans 2-aminocyclopentanesulfonic acid were prepared from cyclohexene and cyclopentene respectively by sulfur monochloride addition, followed by oxidation to 2-chlorosulfonic acid and substitution of chlorine.

Effect of C-ring modifications in benzo[c]quinolizin-3-ones, new selective inhibitors of human 5 alpha-reductase 1.

The synthesis and the inhibition potency of octahydro- and decahydrobenzo[c]quinolizin-3-one derivatives 3--7, as new non-steroidal selective inhibitors of human enzyme 5 alpha-reductase type 1, are reported. These compounds differ from the recently reported benzo[c]quinolizin-3-one inhibitors 2 by the presence of a fully or partially saturated C-ring. Compounds 3 and 4, with a double bond in the C-ring, were prepared by sequential rearrangement-annulation of isoxazolines 19 and 20. C-ring saturated compounds 5--7 were prepared by the Lewis acid-promoted Mannich-Michael tandem reaction of Danishefsky diene with the appropriate N-t-Boc iminium ion. Inhibition experiments were carried out on 5 alpha R-1 and 5 alpha R-2 expressed by CHO cells. Among the prepared compounds, octahydrobenzo[c]quinolizin-3-one 3, with a double bond at the position 6a--10a, was a potent and selective inhibitor of human 5 alpha R-1 (IC(50)=58 nM). The introduction of a tert-butylcarboxyamide at the position 8 (compound 4) was deleterious for the inhibition activity. The lack of the double bond in the C-ring reduced strongly the inhibition activity of compounds 5--7. The extended planarity of the most potent benzo[c]quinolizin-3-ones as well as favorable interactions of the C-ring unsaturation with the enzyme active site could account for the inhibition activity of these compounds.

Oligomers of enantiopure bicyclic gamma/delta-amino acids (BTAa). 1. Synthesis and conformational analysis of 3-aza-6,8-dioxabicyclo

A series of dimeric through pentameric oligomers of a bicyclic gamma/delta-amino acid (BTG) were synthesized using peptide coupling methods in solution with PyBroP or HATU. The analysis of (1)H NMR and CD spectra suggests that these oligomers could have a partially ordered structure in alcohol solutions.