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Context: Polycystic ovary syndrome (PCOS), a highly prevalent endocrine disorder characterized by hyperandrogenism, is the leading cause of anovulatory infertility., Objective: This proof-of-concept study evaluated clinical efficacy and safety of the neurokinin 3 (NK3) receptor antagonist fezolinetant in PCOS., Methods: This was a phase 2a, randomized, double-blind, placebo-controlled, multicenter study (EudraCT 2014-004409-34). The study was conducted at 5 European clinical centers. Women with PCOS participated in the study. Interventions included fezolinetant 60 or 180 mg/day or placebo for 12 weeks. The primary efficacy end point was change in total testosterone. Gonadotropins, ovarian hormones, safety and tolerability were also assessed., Results: Seventy-three women were randomly assigned, and 64 participants completed the study. Adjusted mean (SE) changes in total testosterone from baseline to week 12 for fezolinetant 180 and 60 mg/day were -0.80 (0.13) and -0.39 (0.12) nmol/L vs -0.05 (0.10) nmol/L with placebo (P < .001 and P < .05, respectively). Adjusted mean (SE) changes from baseline in luteinizing hormone (LH) for fezolinetant 180 and 60 mg/d were -10.17 (1.28) and -8.21 (1.18) vs -3.16 (1.04) IU/L with placebo (P < .001 and P = .002); corresponding changes in follicle-stimulating hormone (FSH) were -1.46 (0.32) and -0.92 (0.30) vs -0.57 (0.26) IU/L (P = .03 and P = .38), underpinning a dose-dependent decrease in the LH-to-FSH ratio vs placebo (P < .001). Circulating levels of progesterone and estradiol did not change significantly vs placebo (P > .10). Fezolinetant was well tolerated., Conclusion: Fezolinetant had a sustained effect to suppress hyperandrogenism and reduce the LH-to-FSH ratio in women with PCOS., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Endocrine Society.)

Structure- and ligand-based virtual-screening methods (docking, 2D- and 3D-similarity searching) were analyzed for their effectiveness in virtual screening against FFAR2. To evaluate the performance of these methods, retrospective virtual screening was performed. Statistical quality of the methods was evaluated by BEDROC and RIE. The results revealed that electrostatic similarity search protocol using EON (ET combo) outperformed all other protocols with outstanding enrichment of >95% in top 1% and 2% of the dataset with an AUC of 0.958. Interestingly, the hit lists that are obtained from different virtual-screening methods are generally highly complementary to hits found from electrostatic similarity searching. These results suggest that considering electrostatic similarity searching first increases the chance of identifying more (and more diverse) active compounds from a virtual-screening campaign. Accordingly, prospective virtual screening using electrostatic similarity searching was used to identify novel FFAR2 ligands. The discovered compounds provide new chemical matter starting points for the initiation of a medicinal chemistry campaign., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background & Aims: Intestinal microbes and their metabolites affect the development of colorectal cancer (CRC). Short-chain fatty acids are metabolites generated by intestinal microbes from dietary fiber. We investigated the mechanisms by which free fatty acid receptor 2 (FFAR2), a receptor for short-chain fatty acids that can affect the composition of the intestinal microbiome, contributes to the pathogenesis of CRC., Methods: We performed studies with Apc Min/+ mice, Apc Min/+ Ffar2 -/- mice, mice with conditional disruption of Ffar2 in dendritic cells (DCs) (Ffar2 fl/fl CD11c-Cre mice), Apc Min/+ Ffar2 fl/fl CD11c-Cre mice, and Ffar2 fl/fl mice (controls); some mice were given dextran sodium sulfate to induce colitis, with or without a FFAR2 agonist or an antibody against interleukin 27 (IL27). Colon and tumor tissues were analyzed by histology, quantitative polymerase chain reaction, and 16S ribosomal RNA gene sequencing; lamina propria and mesenteric lymph node tissues were analyzed by RNA sequencing and flow cytometry. Intestinal permeability was measured after gavage with fluorescently labeled dextran. We collected data on colorectal tumors from The Cancer Genome Atlas., Results: Apc Min/+ Ffar2 -/- mice developed significantly more spontaneous colon tumors than Apc Min/+ mice and had increased gut permeability before tumor development, associated with reduced expression of E-cadherin. Colon tumors from Apc Min/+ Ffar2 -/- mice had a higher number of bacteria than tumors from Apc Min/+ mice, as well as higher frequencies of CD39 + CD8 + T cells and exhausted or dying T cells. DCs from Apc Min/+ Ffar2 -/- mice had an altered state of activation, increased death, and higher production of IL27. Administration of an antibody against IL27 reduced the numbers of colon tumors in Apc Min/+ mice with colitis. Frequencies of CD39 + CD8 + T cells and IL27 + DCs were increased in colon lamina propria from Ffar2 fl/fl CD11c-Cre mice with colitis compared with control mice or mice without colitis. Apc Min/+ Ffar2 fl/fl CD11c-Cre mice developed even more tumors than Apc Min/+ Ffar2 fl/fl mice, and their tumors had even higher numbers of IL27 + DCs. Apc Min/+ mice with colitis given the FFAR2 agonist developed fewer colon tumors, with fewer IL27 + DCs, than mice not given the agonist. DCs incubated with the FFAR2 agonist no longer had gene expression patterns associated with activation or IL27 production., Conclusions: Loss of FFAR2 promotes colon tumorigenesis in mice by reducing gut barrier integrity, increasing tumor bacterial load, promoting exhaustion of CD8 + T cells, and overactivating DCs, leading to their death. Antibodies against IL27 and an FFAR2 agonist reduce tumorigenesis in mice and might be developed for the treatment of CRC., (Copyright © 2020 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Context: The thermoregulatory center in the hypothalamus is stimulated by neurokinin 3 receptor (NK3R) activation and inhibited by estrogen-negative feedback. This balance is disrupted in menopause, producing vasomotor symptoms (VMSs)., Objective: To evaluate safety and efficacy of the NK3R antagonist fezolinetant in menopausal VMSs., Design: Twelve-week, double-blind, randomized, placebo-controlled study., Setting: Eight Belgian centers from September 2015 to October 2016., Participants: Generally healthy menopausal women aged 40 to 65 years with moderate/severe VMSs., Interventions: Subjects were randomized (1:1) to 90 mg of fezolinetant twice daily or placebo for 12 weeks., Main Outcome Measures: Subjects captured VMS severity and frequency using an electronic diary. The primary outcome was change from baseline to week 12 in total VMS score with fezolinetant vs placebo. Secondary outcomes included timing of changes in frequency and severity of moderate/severe VMSs and quality-of-life assessments at weeks 4, 8, and 12. Pharmacodynamic and pharmacokinetic effects were assessed, as were safety and tolerability., Results: Of 122 subjects screened, 87 were randomized and 80 (92%) completed the study. At week 12, fezolinetant significantly reduced total VMS score vs placebo (-26.5 vs -12.2, P < 0.001) and decreased mean frequency of moderate/severe VMSs by five episodes per day vs placebo. Severity and frequency of moderate/severe VMSs were reduced from the first day of treatment. Improvements were achieved in all quality-of-life measures. Fezolinetant was well tolerated. The most common fezolinetant-related adverse event was gastrointestinal disorder (n = 6)., Conclusions: Fezolinetant rapidly and significantly reduced moderate/severe VMSs, supporting its potential as an effective nonhormonal treatment option for menopausal women., (Copyright © 2019 Endocrine Society.)

Group 3 innate lymphoid cells (ILC3s) sense environmental signals that are critical for gut homeostasis and host defense. However, the metabolite-sensing G-protein-coupled receptors that regulate colonic ILC3s remain poorly understood. We found that colonic ILC3s expressed Ffar2, a microbial metabolite-sensing receptor, and that Ffar2 agonism promoted ILC3 expansion and function. Deficiency of Ffar2 in ILC3s decreased their in situ proliferation and ILC3-derived interleukin-22 (IL-22) production. This led to impaired gut epithelial function characterized by altered mucus-associated proteins and antimicrobial peptides and increased susceptibility to colonic injury and bacterial infection. Ffar2 increased IL-22 + CCR6 + ILC3s and influenced ILC3 abundance in colonic lymphoid tissues. Ffar2 agonism differentially activated AKT or ERK signaling and increased ILC3-derived IL-22 via an AKT and STAT3 axis. Our findings suggest that Ffar2 regulates colonic ILC3 proliferation and function, and they identify an ILC3-receptor signaling pathway modulating gut homeostasis and pathogen defense., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Free fatty acid-2 (FFA2) receptor is a G-protein coupled receptor of interest in the development of therapeutics in metabolic and inflammatory disease areas. The discovery and optimization of an N-thiazolylamide carboxylic acid FFA2 agonist scaffold is described. Dual key objectives were to i) evaluate the potential of this scaffold for lead optimization in particular with respect to safety de-risking physicochemical properties, i.e. lipophilicity and aromatic content, and ii) to demonstrate the utility of selected lead analogues from this scaffold in a pertinent in vivo model such as oral glucose tolerance test (OGTT). As such, a concomitant improvement in bioactivity together with lipophilic ligand efficiency (LLE) and fraction sp 3 content (Fsp 3 ) parameters guided these efforts. Compound 10 was advanced into studies in mice on the basis of its optimized profile vs initial lead 1 (ΔLLE = 0.3, ΔFsp 3  = 0.24). Although active in OGTT, 10 also displayed similar activity in the FFA2-knockout mice. Given this off-target OGTT effect, we discontinued development of this FFA2 agonist scaffold., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Context: Women's health disorders are commonly treated by agents that suppress the hypothalamic-pituitary-gonadal axis. NK3 receptor antagonism modulates this axis with distinct pharmacology compared to existing therapies., Objective: The study aim was to evaluate safety, pharmacokinetics, and pharmacodynamics on gonadotropins and sex hormones after single- and multiple-dose administration of an NK3R antagonist to healthy men and women., Design and Setting: This was a first-in-human, double-blind, placebo-controlled, combined single and multiple ascending dose trial., Participants: Forty-one men and 24 regularly cycling women participated in the study., Intervention(s): In part 1 of the study, men received single oral doses of 3-180 mg or placebo. In part 2, men received placebo or 20, 60, or 180 mg each day for 10 days. In part 3, women received placebo or 20, 60, or 180 mg each day for 21 days, where dosing was initiated on day 3 ± 2 after menses., Main Outcome Measure(s): Safety, tolerability, pharmacokinetics, and pharmacodynamics on circulating levels of LH, FSH, testosterone, estradiol, and progesterone, in addition to physiological biomarkers of endometrial thickening, follicle growth, and the duration of the menstrual cycle were evaluated., Results: ESN364 was well-tolerated and rapidly bioavailable with linear pharmacokinetics and no drug accumulation with repeated, daily oral administration. Drug treatment dose-dependently decreased basal LH, but not FSH, and consequently decreased estradiol and progesterone (in women) as well as testosterone (in men). The hormonal changes in women corresponded to delayed ovulation, decreased endometrial thickening, impeded follicular maturation, and prolongation of the menstrual cycle. Drug effects were rapidly reversible., Conclusions: Oral administration of the NK3R antagonist, ESN364, suppressed the hypothalamic-pituitary-gonadal axis in healthy volunteers by selective modulation of gonadotropin secretion, leading to a restrained decrease in ovarian hormone levels in women. These results suggest that ESN364 may offer therapeutic benefit in the treatment of women's health disorders with a mitigated risk of menopausal-like adverse events.

Women's health disorders such as uterine fibroids and endometriosis are currently treated by GnRH modulators that effectively suppress the hypothalamic-pituitary-gonadal axis. The neurokinin-3 receptor (NK3R) is an alternative target with an important role in the modulation of this axis. In this report, we demonstrate that systemic administration of an NK3R antagonist (ESN364) prolongs the LH interpulse interval in ovarectomized ewes and significantly lowers plasma LH and FSH concentrations in castrated nonhuman primates (Macaca fascicularis). Moreover, daily oral dosing of ESN364 throughout the menstrual cycle in M fascicularis lowered plasma estradiol levels in a dose-dependent manner, although nadir levels of estradiol were maintained well above menopausal levels. Nevertheless, estradiol levels during the follicular phase were sufficiently inhibited at all doses to preclude the triggering of ovulation as evidenced by the absence of the LH surge and failure of a subsequent luteal phase rise in plasma progesterone concentrations, consistent with the absence of normal cycle changes in the uterus. Apart from the point at surge, FSH levels were not altered over the course of the menstrual cycle. These effects of ESN364 were reversible upon cessation of drug treatment. Together these data support the proposed role of neurokinin B-NK3R signaling in the control of pulsatile GnRH secretion. Furthermore, in contrast to GnRH antagonists, NK3R antagonists induce a partial suppression of estradiol and thereby offer a viable therapeutic approach to the treatment of ovarian sex hormone disorders with a mitigated risk of menopausal-like adverse events in response to long-term drug exposure.

Further lead optimization on N-acyl-triazolopiperazine antagonists to the neurokinin-3 receptor (NK3R) based on the concurrent improvement in bioactivity and ligand lipophilic efficiency (LLE) is reported. Overall, compound 3 (LLE > 6) emerged as the most efficacious in castrated rat and monkey to lower plasma LH, and it displayed the best off-target safety profile that led to its clinical candidate nomination for the treatment of sex-hormone disorders.

Neurokinin-3 receptor (NK3R) has recently emerged as important in modulating the tonic pulsatile gonadotropin-releasing hormone (GnRH) release. We therefore decided to explore NK3R antagonists as therapeutics for sex-hormone disorders that can potentially benefit from lowering GnRH pulsatility with consequent diminished levels of plasma luteinizing hormone (LH) and correspondingly attenuated levels of circulating androgens and estrogens. The discovery and lead optimization of a novel N-acyl-triazolopiperazine NK3R antagonist chemotype achieved through bioisosteric lead change from the high-throughput screening (HTS) hit is described. A concomitant improvement in the antagonist bioactivity and ligand lipophilic efficiency (LLE) parameter were the principal guidelines in the lead optimization efforts. Examples of advanced lead analogues to demonstrate the amenability of this chemotype to achieving a suitable pharmacokinetic (PK) profile are provided as well as pharmacokinetic-pharmacodynamic (PKPD) correlations to analyze the trends observed for LH inhibition in castrated rats and monkeys that served as preliminary in vivo efficacy models.

High-throughput screening of Tranzyme Pharma's proprietary macrocycle library using the aequorin Ca2+-bioluminescence assay against the human ghrelin receptor (GRLN) led to the discovery of novel agonists against this G-protein coupled receptor. Early hits such as 1 (Ki=86 nM, EC50=134 nM) though potent in vitro displayed poor pharmacokinetic properties that required optimization. While such macrocycles are not fully rule-of-five compliant, principally due to their molecular weight and clogP, optimization of their pharmacokinetic properties proved feasible largely through conformational rigidification. Extensive SAR led to the identification of 2 (Ki=16 nM, EC50=29 nM), also known as ulimorelin or TZP-101, which has progressed to phase III human clinical trials for the treatment of postoperative ileus. X-ray structure and detailed NMR studies indicated a rigid peptidomimetic portion in 2 that is best defined as a nonideal type-I' β-turn. Compound 2 is 24% orally bioavailable in both rats and monkeys. Despite its potency, in vitro and in gastric emptying studies, 2 did not induce growth hormone (GH) release in rats, thus demarcating the GH versus GI pharmacology of GRLN.

A series of 3-aryl-5-acylpiperazinyl-pyrazoles (e.g., 3a-b) initially identified through a high-throughput screening campaign using the aequorin Ca(2+) bioluminescence assay as novel, potent small molecule antagonists of the G protein-coupled human tachykinin NK(3) receptor (hNK3-R) is described. Preliminary profiling revealed poor plasma and metabolic stability for these structures in rodents. Further optimization efforts resulted in analogs with improved potency, stability, and pharmacokinetic properties as well as good brain permeability, for example, compounds 26 and 42. Unexpected cytotoxicity was observed in such N-Me pyrazole structures as compounds 41-42., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Ghrelin, the natural ligand of the growth hormone secretagogue receptor (ghrelin receptor), is an orexigenic gut hormone with prokinetic action in the upper gastrointestinal tract. Previously we have shown in a rodent model of postoperative ileus that the synthetic ghrelin receptor agonist TZP-101 prevents the delay in gastric emptying and improves small intestinal transit. The goal of the present study was to investigate whether TZP-101 affects colonic transit and food intake in rats with postoperative ileus. Fasted rats were treated with morphine and subjected to laparotomy under isoflurane anesthesia. Following surgery the animals were placed in clean home cages and fecal pellet output and food intake were monitored for 48 h. TZP-101 or vehicle were administered as 3 i.v. bolus infusions at 0 h, 2 h and 4 h post-surgery. TZP-101 (0.03-1 mg/kg) dose-dependently decreased the time to first bowel movement and increased fecal pellet output measured at 12 h and 24 h post-surgery compared to the vehicle. The administration of TZP-101 was not associated with a significant alteration in food intake. In conclusion, this study provides the first experimental evidence that a novel ghrelin receptor agonist improves large bowel function in rats with postoperative ileus, suggesting that TZP-101 may be useful in the clinic to accelerate upper gastrointestinal transit and to shorten the time to the first bowel movement following surgery.

The peptide hormone ghrelin exerts a wide spectrum of activities including the stimulation of GH release, feeding, and gastrointestinal motility, purportedly via the activation of a common receptor, GH secretagogue receptor (since renamed the GRLN-R) The aim of the present study was to determine whether these effects can be separated pharmacologically. Tranzyme Pharma (TZP)-101 is a small-molecule agonist with potent binding affinity (inhibitory constant = 16 nm) and full agonist activity (EC50 = 29 nm, maximum response = 111%) at the human recombinant GRLN-R. Pharmacokinetic profiling of TZP-101 in rat determined a plasma elimination half-life of 99 min and low blood-brain barrier permeability (0.09%). The pharmacological response to TZP-101, administered centrally [intracerebroventricular (icv)] or peripherally (iv), was evaluated in comparison with that of acylated ghrelin. Thus, TZP-101 (iv) accelerated gastric emptying of a liquid meal (2% methylcellulose) similarly to ghrelin (iv). IAlso, TZP-101 (icv) stimulated spontaneous, cumulative food intake in a similar manner to ghrelin (icv). However, unlike ghrelin, TZP-101 did not elicit significant GH release on either central or peripheral administration. Moreover, TZP-101 did not alter ghrelin-induced GH release. n total, these data demonstrate that the GH response can be pharmacologically demarcated from the orexigenic and gastrointestinal responses to ghrelin in rats. The observation that the centrally mediated orexigenic response and the peripherally mediated gastric motility response are pharmacologically associated is consistent with the classification of ghrelin as a brain-gut peptide, whereas the additional action of ghrelin to stimulate GH release (possibly via a distinct signaling pathway) may be considered a complementary mechanism to harmonize somatic growth and body composition with the regulation of energy homeostasis.

A new method for solid phase parallel synthesis of chemically and conformationally diverse macrocyclic peptidomimetics is reported. A key feature of the method is access to broad chemical and conformational diversity. Synthesis and mechanistic studies on the macrocyclization step are reported.

Postoperative ileus (POI) is a major cause of postoperative complications and prolonged hospitalization. Ghrelin, which is the endogenous ligand for the growth hormone secretagogue receptor, has been found to stimulate gastric motility and accelerate gastric emptying. The present study investigates whether TZP-101 (0.03-1 mg/kg i.v.), a synthetic ghrelin-receptor agonist, could improve gastrointestinal transit in rats with POI. Since the main factors for the development of POI are the surgical manipulation and the gastrointestinal effects of opioid-receptor agonists used for pain management, the effect of TZP-101 was investigated in rats subjected to surgery, to morphine treatment (3 mg/kg s.c.), or to a combination of both. The results showed that TZP-101 is equally effective against the delayed gastrointestinal transit induced by surgery, by morphine, or by the combination of both interventions. The prokinetic action of TZP-101 was more pronounced in the stomach compared to the small intestine.

A convergent synthetic methodology has been developed to access both (2S)- and (2R)-3-fluoroalanine and their corresponding N-methyl analogues, in optically pure form, through a common oxazolidinone intermediate that can be obtained from L- or D-serine. In addition, a procedure for incorporation of these unnatural amino acids in peptide scaffolds is also disclosed herein that minimizes the occurrence of beta-elimination during amide bond formation. [reaction: see text]

A novel class of macrocyclic peptidomimetics was identified and optimized as potent antagonists to the human motilin receptor (hMOT-R). Well-defined structure-activity relationships allowed for rapid optimization of potency that eventually led to high affinity antagonists to hMOT-R. Potency and antagonist functional activity were confirmed both in functional and cell-based assays, as well as on isolated rabbit intestinal smooth muscle strips. Rapid access to this novel class of macrocyclic target structures was made possible through two efficient and complementary solid-phase parallel synthetic approaches, both of which are reported herein.

[reaction: see text]. A two-step synthesis of N-protected unsaturated amino alcohols is disclosed that relies on an unexpectedly selective cross-metathesis (CM) involving allyl cyanide and pent-4-en-1-ol. The solution concentration and the identity of the Ru complex used are critical to the selectivity and efficiency of CM reactions. The intermediate obtained by CM is converted efficiently to the final desired products through a one-pot nitrile reduction/amine protection procedure.

This article describes the design and optimization of a simple three-component aza[4+2]/allylboration reaction to access polysubstituted alpha-hydroxyalkyl piperidines in a highly diastereocontrolled fashion from maleimides, 4-boronohydrazonodienes, and aldehydes. The aldehyde component does not interfere with the first aza[4+2] step, and it was found that this tandem reaction provides better yields of piperidine products 5 when carried out in one-pot. The required 4-borono-hydrazonodienes 1 are synthesized efficiently from the condensation of 3-boronoacrolein pinacol ester (4) with hydrazines. Overall, the three-component process using N-substituted maleimides as dienophiles produces four stereogenic centers and is quite general. It tolerates the use of a wide variety of aldehydes and hydrazine precursors with different electronic and steric characteristics. By allowing such a wide substrate scope and up to four elements of diversity, this reaction process is particularly well adapted towards applications in diversity-oriented synthesis of polysubstituted piperidine derivatives. The suitability of the aza[4+2]/allylboration reaction for use in solid-phase chemistry was also demonstrated using a N-arylmaleidobenzoic acid functionalized resin. This novel multicomponent reaction thus offers a high level of stereocontrol and versatility in the preparation of densely functionalized nitrogen heterocycles.

[reaction: see text]. An efficient solid-phase synthesis of polymer-supported N-arylmaleimides has been developed. Various N-arylmaleimidobenzoic acids (MBA) were elaborated onto Rink and SASRIN resins by reaction of the aniline precursors with maleic anhydride followed by facile cyclative dehydration of the resulting maleimic acids. Applications of these acid-cleavable MBA resins in the solid-phase synthesis of highly decorated pyrrolidines and as thiol scavengers are presented.

Our interest in higher nuclearity sulfido-bridged Fe-S clusters, because of their occurrence in several proteins including nitrogenase, prompted us to investigate the solution chemistry of the functionalized cluster [Fe(4)S(4)(SH)(4)](2)(-) (1). (n-Pr(4)N)(2)[1] crystallizes in space group P2(1)/n of the monoclinic system with a = 26.201(1) Å, b = 11.4999(5) Å, c = 28.090(1) Å, and beta = 110.735(1) degrees. The X-ray structure reveals the conventional cubane-type geometry with an [Fe(4)S(4)](2+) core symmetry more closely approaching T(d)() than the tetragonally distorted D(2)(d)() symmetry reported for the (PPh(4))(2)[1] (Müller, A.; Schladerbeck, N. H.; Bögge, H. J. Chem. Soc., Chem. Commun. 1987, 35). In solution, 1 exists in dynamic equilibrium with self-condensation products formed through elimination of H(2)S and formation of sulfido-bridged cluster oligomers, one of which (4) is prevalent. The self-condensation equilibrium is shifted toward cluster 1. When acetonitrile solutions of 1 were treated with thiols more acidic than H(2)S, it was possible to detect hydrosulfido terminal ligand substitution products of 1 as well as those of the major self-condensation product 4. Detailed analysis of the products in acetonitrile solutions of 1, as well as those generated in solutions of 1 treated with acidic thiol, by electrospray mass spectrometry, and both (19)F and (1)H NMR spectroscopy indicates the presence of a sulfido-bridged acyclic trimer of [Fe(4)S(4)](2+) clusters, i.e. {[Fe(4)S(4)(SH)(3)](2)[Fe(4)S(4)(SH)(2)](&mgr;-S)(2)}(6)(-) (4), a hitherto unprecedented Fe-S structural pattern, as the principal Fe-S cluster self-condensation product.

Attempts to prepare tris(ligand) metal complexes of technetium in intermediate oxidation states with potentially bidentate oxazoline- and thiazoline-containing ligands were unsuccessful; when pertechnetate was reduced in the presence of excess ligand, TcO(2).xH(2)O was produced. Instead, by reaction with preformed M.O cores, a series of oxotechnetium(V) and oxorhenium(V) complexes of the formula MOXL(2) (M = Re, X = Br; M = Tc, X = Cl) and HL = 2-(2'-hydroxyphenyl)-2-oxazoline (Hoz), 2-(2'-hydroxy-3'-methylphenyl)-2-oxazoline (Hmoz), 2-(2'-hydroxyphenyl)-2-thiazoline (Hthoz), and 2-(2'-hydroxyphenyl)-2-benzoxazoline (Hhbo) have been prepared. These compounds have been characterized by a variety of techniques including single-crystal X-ray diffraction. Crystals of Hthoz (C(9)H(9)NOS) are monoclinic, with space group P2(1)/n, a = 7.5342(6) Å, b = 12.2187(6) Å, c = 9.3942(8) Å, beta = 94.233(7) degrees, and Z = 4; those of TcOCl(thoz)(2) (C(18)H(16)ClN(2)O(3)S(2)Tc) are monoclinic, with space group P2(1)/n, a = 16.506(1) Å, b = 7.664(1) Å, c = 16.3216(6) Å, beta = 111.154(4) degrees, and Z = 4; those of ReOBr(oz)(2) (C(18)H(16)BrN(2)O(5)Re) are orthorhombic, with space group Pbca, a = 12.864(2) Å, b = 25.369(2) Å, c = 11.025(2) Å, and Z = 8. The structures were solved by direct (Hthoz) or Patterson (metal complexes) methods and were refined by full-matrix least-squares procedures to R = 0.033, 0.032, and 0.028 for 1600, 3152, and 2651 reflections with I >/= 3sigma(I), respectively. In the two complexes, the geometry around the metals is distorted octahedral with the halide ligands in each bound cis, and one phenolate oxygen from one ligand in each bound trans to the metal-oxo linkage. In ReOBr(oz)(2), the two oxazoline nitrogens are coordinated trans to one another; in TcOCl(thoz)(2), the two thiazoline nitrogens are found cis to one another.