Facile synthesis of α-methylidene-γ-butyrolactones: intramolecular Rauhut–Currier reaction promoted by chiral acid–base organocatalysts

The acid–base organocatalyzed intramolecular Rauhut–Currier (RC) reaction of the dienone enolates has been developed. The enantioselective RC process produces the highly functionalized α-methylidene-γ-butyrolactones as a single diastereomer with up to 98% ee.     

31P Sold-State NMR Investigations on Phosphonic Acids and Phosphonates

Abstract

As known from ³¹P solid-state NMR investigations of inorganic phosphates there is a correlation between chemical shift anisotropy parameters and crystal lattice parameters. For phosphonic acids and phosphonates similar correlations are not known.     

1H-, 13C-UND 31P-NMR-SPEKTROSKOPISCHE UNTERSUCHUNGEN AN BIS-(DIALKOXYTHIOPHOSPHORYL)-UND-(DIALKOXYPHOSPHORYL)-SULFANEN UND-POLYSULFANEN

Abstract

Compounds of the following structure

(R¹O)₂(X)P[sbnd]Y–P(X)(OR²)₂

(X = O, Y = S_n (n = 1–4), R¹ = R² = Me, iPr;

X = S, Y = S_n (n = 1–4), R¹, R² = Me, Et, iPr, iBu;

X = S, Y = S-Se-S, S-Te-S, R¹ = R² = Me

were prepared and their NMR spectra were analysed. Depending on the number of sulfur atoms, bonded between the phosphorus atoms, typical ranges of the P-P coupling constants were found for the different sulfanes investigated: ²J_PP from-10 to-20 Hz, ³J_PP less than 3 Hz, ⁴J_PP from +10 to +13 Hz and ⁵J_PP less than 1 Hz. For the small vicinal coupling constants and the relatively large values of ⁴J_PP different possibilities of their interpretation are given.     

Direct Targeting of Rab‐GTPase–Effector Interactions

Small GTPases are molecular switches using GDP/GTP alternation to control numerous vital cellular processes. Although aberrant function and regulation of GTPases are implicated in various human diseases, direct targeting of this class of proteins has proven difficult, as GTPase signaling and regulation is mediated by extensive and shallow protein interfaces. Here we report the development of inhibitors of protein–protein interactions involving Rab proteins, a subfamily of GTPases, which are key regulators of vesicular transport. Hydrocarbon‐stapled peptides were designed based on crystal structures of Rab proteins bound to their interaction partners. These modified peptides exhibit significantly increased affinities and include a stapled peptide (StRIP3) that selectively binds to activated Rab8a and inhibits a Rab8a–effector interaction in vitro.