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Threonylcarbamoyladenosine (t(6)A) is a universal modification found at position 37 of ANN decoding tRNAs, which imparts a unique structure to the anticodon loop enhancing its binding to ribosomes in vitro. Using a combination of bioinformatic, genetic, structural and biochemical approaches, the universal protein family YrdC/Sua5 (COG0009) was shown to be involved in the biosynthesis of this hypermodified base. Contradictory reports on the essentiality of both the yrdC wild-type gene of Escherichia coli and the SUA5 wild-type gene of Saccharomyces cerevisiae led us to reconstruct null alleles for both genes and prove that yrdC is essential in E. coli, whereas SUA5 is dispensable in yeast but results in severe growth phenotypes. Structural and biochemical analyses revealed that the E. coli YrdC protein binds ATP and preferentially binds RNA(Thr) lacking only the t(6)A modification. This work lays the foundation for elucidating the function of a protein family found in every sequenced genome to date and understanding the role of t(6)A in vivo.

[reaction: see text]. Feeding experiments using a deuterium labeled C16 maleic anhydride and whole cell culture of ATCC 74256 led to the isolation of phomoidride B with deuterium incorporation at C(7) and C(19) as determined by 2H NMR and electrospray mass spectrometry. This result is in accord with a decarboxylative homodimerization of the C16 maleic anhydride as a key biosynthetic step leading to phomoidride B.

Crude Pseudomonas cepacia lipase (Amano PS-30) is a suitable biocatalyst for the kinetic resolution of the 1,2- cis -disubstituted cyclopentanoid building block (3a R *,4 R *,6a S *)-(±)-4-hydroxymethyl-3,3a,4,6a-tetrahydrocyclopenta[ b ]furan-2-one through enantioselective transesterification. Enantiomerically enriched acetic acid (3a S ,4 S ,6a R )-(+)-2-oxo-3,3a,4,6a-tetrahydro-2 H -cyclopenta[ b ]furan-4-yl methyl ester was utilized in a formal synthesis of the iridoids (+)-isoiridomyrmecin and (−)-teucriumlactone.

Palladium-catalyzed cross coupling of aryl bromides and silylketene acetals in the presence of tributyltin fluoride or copper(II) fluoride is described.

[structure: see text] Fermentation of ATCC 74256 led to the isolation and identification of C7 epimers of phomoidride A (CP-225,917) and phomoidride B (CP-263,114). We suggest the names phomoidrides C and D for these new fermentation products. Studies on the effect of pH on the distribution of phomoidrides A-D suggest phomoidride B (CP-263,114) is the first-formed secondary metabolite and the source of the remaining three phomoidrides.

[structure: see text] Fermentation of ATCC 74256 led to the isolation and identification of C7 epimers of phomoidride A (CP-225,917) and phomoidride B (CP-263,114). We suggest the names phomoidrides C and D for these new fermentation products. Studies on the effect of pH on the distribution of phomoidrides A-D suggest phomoidride B (CP-263,114) is the first-formed secondary metabolite and the source of the remaining three phomoidrides.

[reaction: see text]. An intramolecular cyclization strategy for effecting a biomimetic synthesis of the core structure of the fungal secondary metabolites phomoidrides A and B is described. The cyclization substrate 20 is prepared in eight steps from dibromide 10. Treatment of 20 with triethylamine in acetonitrile results in a rapid cyclization to give 21 and 22 in good yield.

A biosynthesis of the structurally complex nonadride CP-225,917 (1) is outlined. A key step in this proposal is the dimerization of a C(16) anhydride derived from the condensation of lauric acid and oxaloacetic acid. An important element of this step is a templating effect imposed by two thioester linkages, reminiscent of a polyketide or fatty acid synthase pathway. On the basis of this principle, the dimerization of two C(11) anhydrides, templated by a 1,n-diol tether, leading to the core structure of CP-225,917 and CP-263,114 was investigated.