ABSTRACT
[reaction: see text]. Radical cyclization of 6 affords the bicyclic vinyl ether 9 with the appropriate stereochemistry for elaboration (seven steps) to griseolic acid B (1).
Subject(s)
Adenosine/analogs & derivatives , Adenosine/chemical synthesis , Phosphodiesterase Inhibitors/chemical synthesis , 3',5'-Cyclic-AMP Phosphodiesterases/antagonists & inhibitors , Cyclization , Indicators and Reagents , Magnetic Resonance Spectroscopy , Oxidation-Reduction , Stereoisomerism , Streptomyces/chemistryABSTRACT
The liposidomycins comprise a family of complex nucleoside antibiotics that inhibit bacterial peptidoglycan synthesis. Their structures (1, 2) feature nucleoside, ribofuranoside, diazepanone, and lipid regions. Several stereogenic centers remain unassigned, including three within the diazepanone region: C-6', C-2'", and C-3'". An intramolecular reductive amination reaction has been used to prepare model diazepanones. Analysis of 40 and two of its diastereomers by NMR spectroscopy, X-ray crystallography, and molecular modeling indicates a close relative configurational and conformational match between 40 and the liposidomycin diazepanone degradation product 43 and allows the assignment of stereochemistry of the natural products as either [C-6'(R), C-2'"(R), C-3'"(R)] or [C-6'(S), C-2'"(S), C-3'"(S)].
Subject(s)
Aminoglycosides , Anti-Bacterial Agents/chemical synthesis , Amination , Anti-Bacterial Agents/chemistry , Models, Molecular , Molecular Conformation , Oxidation-Reduction , Stereoisomerism , Valine/analogs & derivatives , Valine/chemistryABSTRACT
N-Substituted nipecotic and iso-nipecotic amides of beta-methylTrpLys tert-butyl ester were found to be novel, selective and potent agonists of the somatostatin subtype-2 receptor in vitro. For example iso-nipecotic amide 8a showed high hsst2 binding affinity (Ki = 0.5 nM) and good selectivity (h5/h2 = 832).
Subject(s)
Nipecotic Acids/metabolism , Receptors, Somatostatin/agonists , Animals , Combinatorial Chemistry Techniques , Humans , Isomerism , Nipecotic Acids/chemical synthesis , Oligopeptides/chemical synthesis , Oligopeptides/metabolism , Protein Binding , Receptors, Somatostatin/metabolism , Structure-Activity RelationshipABSTRACT
Synthetic ligands have been identified that reset and amplify the cycle of pulsatile GH secretion by interacting with the orphan GH-secretagogue receptor (GHS-R). The GHS-R is rhodopsin like, but does not obviously belong to any of the established G protein-coupled receptor (GPCR) subfamilies. We recently characterized the closely related orphan family member, GPR38, as the motilin receptor. A common property of both receptors is that they amplify and sustain pulsatile biological responses in the continued presence of their respective ligands. To efficiently identify additional members of this new GPCR family, we explored a vertebrate species having a compact genome, that was evolutionary distant from human, but where functionally important genes were likely to be conserved. Accordingly, three distinct full-length clones, encoding proteins of significant identity to the human GHS-R, were isolated from the Pufferfish (Spheroides nephelus). Southern analyses showed that the three cloned Pufferfish genes are highly conserved across species. The gene with closest identity (58%) was activated by three synthetic ligands that were chosen for their very high selectivity on the GHS-R as illustrated by their specificity in activating the wild-type human GHS-R but not the E124Q mutant. These results indicate that the ligand activation domain of the GHS-R has been evolutionary conserved from Pufferfish to human (400 million years), supporting the notion that the GHS-R and its natural ligand play a fundamentally important role in biology. Furthermore, they illustrate the power of exploiting the compact Pufferfish genome for simplifying the isolation of endocrinologically important receptor families.
Subject(s)
Fishes/genetics , Receptors, Cell Surface/chemistry , Receptors, G-Protein-Coupled , Amino Acid Sequence , Animals , Blotting, Southern , Cell Line , Cloning, Molecular , Conserved Sequence , Genomic Library , Humans , Ligands , Models, Genetic , Molecular Sequence Data , Protein Structure, Tertiary , Receptors, Cell Surface/genetics , Receptors, Ghrelin , Sequence Alignment , Sequence Homology, Amino Acid , TransfectionABSTRACT
A series of structurally diverse growth hormone (GH) releasing substances have been synthesized that are distinct from the naturally occurring GH releasing hormone (GHRH). These synthetic molecules range from the family of GH releasing peptides and mimetics such as MK-0677. The physiological importance of these molecules and their receptor is exemplified by studies in the elderly. For example, when MK-0677 was administered chronically to 70- to 90-year-old subjects, once daily, the age-related reduced amplitude of GH pulses was reversed to that of the physiological profile typical of young adults. In 1996, the synthesis of (35)S-MK-0677 was reported and used as a ligand to characterize a common receptor (GH secretagogue receptor [GHS-R]) for the GH releasing substances. The GHS-R is distinct from the GHRH receptor. Subsequently, the GHS-R gene was cloned and shown to encode a unique G-protein coupled receptor with a deduced protein sequence that was 96% identical in human and rat. Because of the physiological importance of the GHS-R, a search for family members (FMs) was initiated and its molecular evolution investigated. Three FMs GPR38, GPR39 and FM3 were isolated from human genomic libraries. To accelerate the identification of other FMs, a vertebrate organism with a compact genome distant in evolutionary terms from humans was exploited. The pufferfish (Spheroides nephelus) genome provides an ideal model for the discovery of human genes. Three distinct full-length clones encoding proteins of significant sequence identity to the human GHS-R were cloned from the pufferfish. Remarkably, the pufferfish gene with highest sequence homology to the human receptor was activated by the hexapeptide and non-peptide ligands. These intriguing results show that the structure and function of the ligand binding pocket of the human GHS-R has been highly conserved in evolution ( approximately 400 million years) and strongly suggests that an endogenous natural ligand has been conserved. This new information is consistent with a natural ligand for the GHS-R playing a fundamentally important and conserved role in physiology.
Subject(s)
Growth Hormone-Releasing Hormone , Receptors, Cell Surface/physiology , Receptors, G-Protein-Coupled , Aged , Aged, 80 and over , Amino Acid Sequence , Animals , Binding Sites , Human Growth Hormone/metabolism , Humans , Indoles/pharmacology , Molecular Sequence Data , Receptors, Cell Surface/chemistry , Receptors, Cell Surface/metabolism , Receptors, Ghrelin , Receptors, Neuropeptide , Receptors, Pituitary Hormone-Regulating Hormone , Spiro Compounds/pharmacologyABSTRACT
Replacement of the phenyl in 3 with a 2-pyridyl or 4-thiazolyl group resulted in increased potency in the rat pituitary cell GH release assay and in beagles.
Subject(s)
Growth Hormone/chemical synthesis , Growth Hormone/metabolism , Thiazoles/chemical synthesis , Animals , Biological Availability , Dogs , Models, Chemical , Rats , Rats, Sprague-Dawley , Structure-Activity Relationship , Thiazoles/administration & dosage , Thiazoles/pharmacokinetics , Time FactorsSubject(s)
Esters/chemical synthesis , Growth Hormone/metabolism , Piperidines/chemical synthesis , Administration, Oral , Animals , Biological Availability , Crystallography, X-Ray , Dogs , Esters/administration & dosage , Esters/pharmacokinetics , Esters/pharmacology , Growth Hormone/blood , In Vitro Techniques , Male , Piperidines/administration & dosage , Piperidines/pharmacokinetics , Piperidines/pharmacology , Pituitary Gland/cytology , Pituitary Gland/drug effects , Pituitary Gland/metabolism , Rats , Rats, Sprague-Dawley , StereoisomerismABSTRACT
A series of C-terminus capped dipeptides and tripeptides was synthesized as growth hormone (GH) secretagogues. Among them, tripeptide Aib-D-Trp-D-homoPhe-OEt showed low nanomolar activity in the rat pituitary assay. Thus, we have demonstrated that the GH secretagogue activity of the hexa-hepta-GH releasing peptides can be mimicked at the tripeptide level.
Subject(s)
Dipeptides/chemical synthesis , Growth Hormone/metabolism , Oligopeptides/chemical synthesis , Amino Acid Sequence , Animals , Dipeptides/chemistry , Dipeptides/pharmacology , In Vitro Techniques , Models, Molecular , Molecular Structure , Oligopeptides/chemistry , Oligopeptides/pharmacology , Pituitary Gland/metabolism , Rats , Structure-Activity RelationshipABSTRACT
Systematic SAR studies of the different regioisomers and homologues of the spiro(indane-1,4-piperidine) moiety in the growth hormone secretagogue L-162,752 are presented. Among them, spiro(3H-1-benzopyran-2,3-piperidine) was found to afford secretagogues with low nanomolar in vitro activity.
