A synthetic antibiotic class overcoming bacterial multidrug resistance.

The dearth of new medicines effective against antibiotic-resistant bacteria presents a growing global public health concern. For more than five decades, the search for new antibiotics has relied heavily on the chemical modification of natural products (semisynthesis), a method ill-equipped to combat rapidly evolving resistance threats. Semisynthetic modifications are typically of limited scope within polyfunctional antibiotics, usually increase molecular weight, and seldom permit modifications of the underlying scaffold.

Practical Gram-Scale Synthesis of Iboxamycin, a Potent Antibiotic Candidate.

A gram-scale synthesis of iboxamycin, an antibiotic candidate bearing a fused bicyclic amino acid residue, is presented. A pivotal transformation in the route involves an intramolecular hydrosilylation-oxidation sequence to set the ring-fusion stereocenters of the bicyclic scaffold. Other notable features of the synthesis include a high-yielding, highly diastereoselective alkylation of a pseudoephenamine amide, a convergent sp-sp Negishi coupling, and a one-pot transacetalization-reduction reaction to form the target compound's oxepane ring.

Selective Synthesis of Divergolide I.

Divergolide I (1) is a naphthoquinone ansamycin that exhibits broad antibacterial activity. Its tetracyclic ring system is believed to be biosynthetically assembled via ring contraction of a macrocyclic precursor (proto-divergolide) that is both a macrolactone and a macrolactam. We here report a convergent and enantioselective synthesis that delivers the target molecule in less than 20 linear steps.

Sequence variations in 185/333 messages from the purple sea urchin suggest posttranscriptional modifications to increase immune diversity.

The 185/333 gene family is highly expressed in two subsets of immune cells in the purple sea urchin in response to immune challenges. The genes encode a surprisingly diverse set of transcripts, which is a function of the variable presence or absence of blocks of shared sequences, known as elements that generate element patterns. Diversity is also the result of a significant level of point mutations.

Distinctive expression patterns of 185/333 genes in the purple sea urchin, Strongylocentrotus purpuratus: an unexpectedly diverse family of transcripts in response to LPS, beta-1,3-glucan, and dsRNA.

Background: A diverse set of transcripts called 185/333 is strongly expressed in sea urchins responding to immune challenge. Optimal alignments of full-length 185/333 cDNAs requires the insertion of large gaps that define 25 blocks of sequence called elements. The presence or absence of individual elements also defines a specific element pattern for each message.