Total Synthesis of (+)-Prunustatin A: Utility of Organotrifluoroborate-Mediated Prenylation and Shiina MNBA Esterification and Macrolactonization To Avoid a Competing Thorpe-Ingold Effect Accelerated Transesterification.

A convergent total synthesis of (+)-prunustatin A is described through the assembly of two key fragments and a macrolactonization. Shiina MNBA couplings were used for the formation of each of the four ester bonds in the tetralactone ring, including the key macrocyclization which was essential to minimize competing Thorpe-Ingold accelerated transesterification. Other key steps included an organoboron-based prenylation using potassium prenyltrifluoroborate and a carbonyldiimidazole-mediated coupling to form the salicylamide.

Oxazoles revisited: On the nature of binding of benzoxazole and 2-methylbenzoxazole with the zinc and palladium halides.

A synthetic and structural (X-ray) investigation into the bonding modes of benzoxazole (box) and 2-methylbenzoxazole (Mebox) ligands with halide precursors of Zn and Pd has been undertaken to clarify earlier discrepancies concerning the nature of the bonding mode(s) of the two azoles. In four structurally characterised examples, all contain the title ligands in a κ(1)N bonding motif. Calculations at the density functional level (DFT) of theory (B3LYP) confirm the ground state stability of this class of coordination for several hypothetical Pd and Zn (gas phase) compounds. The attempt to obtain suitable crystalline material of PdCl(2)(box)(2) (i.e., 5) leads to substantial complex degradation. One minor product of this process has been identified (X-ray) as the diarylformamidinato complex C(26)H(22)N(4)O(4)Pd, presumably formed via a complex combination of the decomposition products of both free box and 5.