PASK links cellular energy metabolism with a mitotic self-renewal network to establish differentiation competence.

Quiescent stem cells are activated in response to a mechanical or chemical injury to their tissue niche. Activated cells rapidly generate a heterogeneous progenitor population that regenerates the damaged tissues. While the transcriptional cadence that generates heterogeneity is known, the metabolic pathways influencing the transcriptional machinery to establish a heterogeneous progenitor population remains unclear. Here, we describe a novel pathway downstream of mitochondrial glutamine metabolism that confers stem cell heterogeneity and establishes differentiation competence by countering post-mitotic self-renewal machinery. We discovered that mitochondrial glutamine metabolism induces CBP/EP300-dependent acetylation of stem cell-specific kinase, PAS domain-containing kinase (PASK), resulting in its release from cytoplasmic granules and subsequent nuclear migration. In the nucleus, PASK catalytically outcompetes mitotic WDR5-anaphase-promoting complex/cyclosome (APC/C) interaction resulting in the loss of post-mitotic Pax7 expression and exit from self-renewal. In concordance with these findings, genetic or pharmacological inhibition of PASK or glutamine metabolism upregulated Pax7 expression, reduced stem cell heterogeneity, and blocked myogenesis in vitro and muscle regeneration in mice. These results explain a mechanism whereby stem cells co-opt the proliferative functions of glutamine metabolism to generate transcriptional heterogeneity and establish differentiation competence by countering the mitotic self-renewal network via nuclear PASK.

Approaches to the quaternary stereocentre and to the heterocyclic core in diazonamide A using the Heck reaction and related coupling reactions.

In model studies towards the quaternary centre at the heart of diazonamide A (early structure 2; revised structure 1), cyclisations of the alkene-substituted iodoaryls 4, 13, 18 and 23, under Heck reaction conditions, were shown to lead to the corresponding benzodihydrofuran 5, benzofuranone 14 and the oxindoles 19 and 24 respectively, in 50-80% yield. Further manipulation of the benzodihydrofuran 5 then led to the intermediates 30, 33 and 39, which make up parts of the oxazole-indole heterocyclic core in diazonamide A. Attempts to perform a corresponding 13-exo-trig Heck cyclisation from the precursor 46a, prepared from 44 and 45, leading to 47 were not successful. A similar outcome was obtained during attempts to effect Heck cyclisations from the ester 57 and the related ether 59. Treatment of the chromene-substituted iodoaryl 62 with Pd(OAc)2, PPh3 and Ag2CO3 led to the spirocycle 64 as a crystalline solid. X-Ray crystal structure analysis established that the quaternary centre in 64 had the same configuration as that present in diazonamide A (1).

An efficient, palladium-catalyzed, enantioselective synthesis of (2R)-3-butene-1,2-diol and its use in highly selective Heck reactions.

A robust and scalable procedure for the palladium-catalyzed dynamic kinetic asymmetric transformation of 3,4-epoxy-1-butene into (2R)-3-butene-1,2-diol with water as the cosolvent is reported. Examination of the effects of solvent and temperature led to the identification of conditions that permitted use of 0.025 mol % catalyst, providing (2R)-3-butene-1,2-diol in 84% isolated yield and 85% enantiomeric excess. Subsequent Heck reactions with a diverse range of coupling partners are described and the influence of their electronic nature on maintaining the enantiopurity of the diol is discussed.

Highly diastereoselective Simmons-Smith cyclopropanation of allylic amines.

[reaction: see text] Cyclopropanation of allylic tertiary amines using the Simmons-Smith reagent has been achieved by employing chelating groups in close proximity to the amine. The chelating groups promote cyclopropanation at the expense of N-ylide formation. Using pseudoephedrine as the chelating group, high diastereoselectivity is observed.

Tandem formation and [2,3] rearrangement of methylene ammonium ylides derived from amines and the Simmons-Smith reagent.

[reaction: see text] Zinc-complexed methylene ammonium ylides are formed from tertiary amines and the Simmons-Smith reagent. These stable entities can be activated with n-BuLi to allow reactions typical of ammonium ylides such as [2,3] rearrangements. In the case of oxazolidine 12, ylide formation, activation, and subsequent [2,3] rearrangement was highly efficient and occurred with very high diastereoselectivity.