Maf transcription factors constitute a family of the basic region-leucine zipper (bZip) factors and recognize unusually long DNA motifs (13 or 14 bp), termed the Maf recognition element (MARE). The MARE harbors extended GC sequences on each side of its core motif, which is similar to TRE or CRE (7 or 8 bp) recognized by the AP1 and CREB/ATF families, respectively. To ascertain the structural basis governing the acquirement of such unique DNA recognition, we determined the crystal structure of the MafG-DNA complex. Each MafG monomer consists of three helices in which the carboxyl-terminal long helix organizes one DNA-contacting element and one coiled-coil dimer formation element. To our surprise, two well-conserved residues, Arg57 and Asn61 in the basic region, play critical roles in Maf-specific DNA recognition. These two residues show unique side-chain orientations and interact directly with the extended GC bases. Maf-specific residues in the aminoterminal and basic regions appear to indirectly stabilize MARE recognition through DNA backbone phosphate interactions. This study revealed an alternative DNA recognition mechanism of the bZip factors that bestows specific target gene profiles upon Maf homodimers or Maf-containing heterodimers.

The cobalt-catalyzed cross-coupling of alkyl (pseudo)halides with alkyl Grignard reagents in the presence of 1,3-butadiene as a ligand precursor and LiI is described. Sterically congested quaternary carbon centers could be constructed by using tertiary alkyl Grignard reagents. This reaction proceeds via an ionic mechanism with inversion of stereochemistry at the reacting site of the alkyl halide and is compatible with various functional groups. The use of both 1,3-butadiene and LiI was essential for achieving high yields and high selectivities.

An efficient synthesis of a doubly stranded [3]rotaxane has been developed through bridging of a pseudo[3]rotaxane featuring two axle components. Reversible azine formation was effective as the bridging reaction. Kinetic and thermodynamic conditions provided the [2]- and [3]rotaxanes, respectively.

The cross-coupling of alkyl (pseudo)halides with alkyl Grignard reagents is catalyzed efficiently by a cobalt(II) chloride-lithium iodide-1,3-diene catalytic system, which provides a new synthetic tool for constructing sp 3 carbon chains. This system is particularly useful for creating quaternary carbon centers via the use of tertiary alkyl Grignard reagents. Various functional groups including esters, amides and carbamates are well tolerated.

Kinetically and thermodynamically favored [2]rotaxanes, with an axle component positioned within a large and small ring, respectively, were provided by bridging of a [2]pseudorotaxane formed from an unsymmetric mono-crown ether and the ammonium salt.