The carbonyl epoxide rearrangement. A chiral synthesis of the mus musculus pheromone

Asymmetric synthesis of (-)-dehydro-exo-brevicomin with a photoisomerisation-intramolecular acetalisation sequence

We herein report a novel, short asymmetric synthesis of (-)-dehydro-exo-brevicomin (DHB, 1), a sex pheromone isolated from house mice, in 44% overall yield, the highest yield reported so far, over eight steps from trans-3-hexen-1-ol (7). We successfully prepared the target molecule (-)-1 from spontaneous intramolecular acetalisation after the photoisomerisation of trans-enone 6, which generated the corresponding cis-enone 5in situ, the possible biosynthetic precursor of DHB.

Myriaporones 1-4, cytotoxic metabolites from the Mediterranean bryozoan Myriapora truncata

Four novel polyketide-derived metabolites, myriaporones 1, 2, 3, and 4, have been isolated from the Mediterranean bryozoan Myriapora truncata. Their structures and stereochemistry have been assigned from the analysis of spectroscopic data. The inseparable equilibrium mixture of myriaporones 3 and 4 showed 88% inhibition of L1210 murine leukemia cells at 0.2 microg/mL.

Desymmetrization of a centrosymmetric diepoxide: efficient synthesis of a key intermediate in a total synthesis of hemibrevetoxin B

The preparation of an established intermediate in a total synthesis of hemibrevetoxin B is described. The acid-catalyzed cyclization of trans-4,5-epoxyoctane-2,7-dione exhibited a valuable mixture of kinetic and thermodynamic control: stereospecific epoxide opening was followed by equilibration of the products to provide the required trans-fused octahydropyrano[3,2-b]pyran ring system. Two-directional elaboration, by acetal substitution, ozonolysis, and sulfur ylide-mediated epoxidation, provided a centrosymmetric diepoxide. The key step of the synthesis was the first desymmetrization of a centrosymmetric molecule in natural product synthesis: Jacobsen asymmetric epoxide hydrolysis and acetonization provided the known synthetic intermediate in 97% yield and >95% ee over two steps. The exploitation of the center of symmetry of the AB ring system of the natural product contributed greatly to the efficiency (eight steps, 34% overall yield) of the synthesis.

Pheromone binding by polymorphic mouse major urinary proteins

Mouse major urinary proteins (MUPs) have been proposed to play a role in regulating the release and capture of pheromones. Here, we report affinity measurements of five recombinant urinary MUP isoforms (MUPs-I, II, VII, VIII, and IX) and one recombinant nasal isoform (MUP-IV) for each of three pheromonal ligands, (+/-)-2-sec-butyl-4,5-dihydrothiazole (SBT), 6-hydroxy-6-methyl-3-heptanone (HMH), and (+/-)dehydro-exo-brevicomin (DHB). Dissociation constants for all MUP-pheromone pairs were determined by isothermal titration calorimetry, and data for SBT were corroborated by measurements of intrinsic protein fluorescence. We also report the isolation of MUP-IV protein from mouse nasal extracts, in which MUP-IV mRNA has been observed previously. The affinity of each MUP isoform for SBT (K(d) approximately 0.04 to 0.9 micro M) is higher than that for DHB (K(d) approximately 26 to 58 micro M), which in turn is higher than that for HMH (K(d) approximately 50 to 200 micro M). Isoforms I, II, VIII, and IX show very similar affinities for each of the ligands. MUP-VII has approximately twofold higher affinity for SBT but approximately twofold lower affinity for the other pheromones, whereas MUP-IV has approximately 23-fold higher affinity for SBT and approximately fourfold lower affinity for the other pheromones. The variations in ligand affinities of the MUP isoforms are consistent with structural differences in the binding cavities of the isoforms. The data indicate that the concentrations of available pheromones in urine may be influenced by changes in the expression levels of urinary MUPs or the excretion levels of other MUP ligands. The variation in pheromone affinities of the urinary MUP isoforms provides only limited support for the proposal that MUP heterogeneity plays a role in regulating profiles of available pheromones. However, the binding data support the proposed role of nasal MUPs in sequestering pheromones and possibly transporting them to their receptors.

Stereoselectivity in mammalian chemical communication: male mouse pheromones

Two male mouse pheromones, 3,4-dehydro-exo-brevicomin (DHB) and 2-sec-butyldihydrothiazole (SBT), are chiral molecules which were previously tested in their respective bioassays as racemic mixtures. The focus of this study has been to determine the absolute configuration of their natural forms and its relation to stereospecific biological action. DHB was established as the R,R-enantiomer possessing biological activity. Due to an extremely easy racemization of SBT under very mild conditions, enantioselectivity of its transmission and its action at the receptor site appear to be of secondary importance.