ABSTRACT
The Zn(OTf)2-catalyzed domino reaction of enamide-ynamides in the presence of trimethylsilyl cyanide as an external nucleophile to construct spirocyclic indolines was developed. This domino reaction involved cyclization of enamide to ynamide to generate 4',5'-dihydrospiro[indoline-3,3'-pyrrol]-1'-ium followed by cyanide addition to produce spiroindolopyrrolidines with good diastereoselectivity.
ABSTRACT
A Brønsted acid-promoted arene-ynamide cyclization has been developed to construct the 3H-pyrrolo[2,3-c]quinolines. This reaction consists of the generation of a highly reactive keteniminium intermediate from arene-ynamide activated by a Brønsted acid and electrophilic aromatic substitution reaction to give arene-fused quinolines in high yields. This methodology enabled facile access to marinoquinolines A and C and aplidiopsamine A.
Subject(s)
Acids/chemistry , Pyrroles/chemistry , Pyrroles/chemical synthesis , Quinolines/chemistry , Quinolines/chemical synthesis , Catalysis , Cyclization , Molecular StructureABSTRACT
In the yeast, Saccharomyces cerevisiae, cell size is affected by the kind of carbon source in the medium. Here, we present evidence that the Gpr1 receptor and Gpa2 Galpha subunit are required for both maintenance and modulation of cell size in response to glucose. In the presence of glucose, mutants lacking GPR1 or GPA2 gene showed smaller cells than the wild-type strain. Physiological studies revealed that protein synthesis rate was reduced in the mutant strains indicating that reduced growth rate, while the level of mRNAs for CLN1, 2 and 3 was not affected in all strains. Gene chip analysis also revealed a down-regulation in the expression of genes related to biosynthesis of not only protein but also other cellular component in the mutant strains. We also show that GPR1 and GPA2 are required for a rapid increase in cell size in response to glucose. Wild-type cells grown in ethanol quickly increased in size by addition of glucose, while little change was observed in the mutant strains, in which glucose-dependent cell cycle arrest caused by CLN1 repression was somewhat alleviated. Our study indicates that the yeast G-protein coupled receptor system consisting of Gpr1 and Gpa2 regulates cell size by affecting both growth rate and cell division.
Subject(s)
GTP-Binding Protein alpha Subunits/physiology , Glucose/physiology , Receptors, G-Protein-Coupled/physiology , Saccharomyces cerevisiae Proteins/physiology , Saccharomyces cerevisiae/physiology , Cyclins/biosynthesis , Cyclins/genetics , Cyclins/metabolism , G1 Phase/physiology , GTP-Binding Protein alpha Subunits/genetics , Gene Expression Regulation, Bacterial/physiology , Mutation , RNA, Messenger/metabolism , Receptors, G-Protein-Coupled/genetics , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/metabolismABSTRACT
In response to various extracellular signals, the morphology of the human fungal pathogen Candida albicans switches from yeast to hypha form. Here, we report that GPR1 encoding a putative G-protein-coupled receptor and GPA2 encoding a Galpha subunit are required for hypha formation and morphogenesis in C. albicans. Mutants lacking Gpr1 (gpr1/gpr1) or Gpa2 (gpa2/gpa2) are defective in hypha formation and morphogenesis on solid hypha-inducing media. These phenotypic defects in solid cultures are suppressed by exogenously added dibutyryl-cyclic AMP (dibutyryl-cAMP). Biochemical studies also reveal that GPR1 and GPA2 are required for a glucose-dependent increase in cellular cAMP. An epistasis analysis indicates that Gpr1 functions upstream of Gpa2 in the same signaling pathway, and a two-hybrid assay reveals that the carboxyl-terminal tail of Gpr1 interacts with Gpa2. Moreover, expression levels of HWP1 and ECE1, which are cAMP-dependent hypha-specific genes, are reduced in both mutant strains. These findings support a model that Gpr1, as well as Gpa2, regulates hypha formation and morphogenesis in a cAMP-dependent manner. In contrast, GPR1 and GPA2 are not required for hypha formation in liquid fetal bovine serum (FBS) medium. Furthermore, the gpr1 and the gpa2 mutant strains are fully virulent in a mouse infection. These findings suggest that Gpr1 and Gpa2 are involved in the glucose-sensing machinery that regulates morphogenesis and hypha formation in solid media via a cAMP-dependent mechanism, but they are not required for hypha formation in liquid medium or during invasive candidiasis.
