Synthesis of a novel, conformationally restricted analog of tryptophan

Total synthesis of nostodione A, a cyanobacterial metabolite

The first total synthesis of the mitotic spindle poison nostodione A is described. The inherent oxidative sensitivity of indoles is utilized for a late introduction of a second carbonyl to the cyclopent[b]indole-2-one system. The tricyclic system is prepared from indole-3-acetic acid and O-silylated 4-ethynylphenol, using a stereoselective intramolecular reductive Heck cyclization as the key transformation.

An enzymatic cyclopentyl[b]indole formation involved in scytonemin biosynthesis

Previous studies of the biosynthetic enzymes involved in the assembly of scytonemin (1), a cyanobacterial sunscreen, have identified beta-ketoacid 2 as an important intermediate that is produced by ThDP-dependent enzyme ScyA. We now report that ScyC, previously annotated as a hypothetical protein, catalyzes cyclization and decarboxylation of 2 to generate ketone 5. Assembly of the cyclopentyl[b]indole structure in this manner has little precedent in the chemical literature. Additional mechanistic experiments have revealed that cyclization likely precedes decarboxylation and that the latter event may provide a driving force for cyclopentane formation.

Efficient synthesis of 2-aminoindane-2-carboxylic acid via dialkylation of nucleophilic glycine equivalent

An efficient, easy to scale-up method for preparing 2-aminoindane-2-carboxylic acid via two-step alkylation of a Ni(II)-complex of glycine Schiff base with 2-[N-(alpha-picolyl)amino]benzophenone (PAAP) (2b) with o-dibromoxylylene (3) is reported. The first step, monoalkylation of 2b with 3, conducted under phase-transfer conditions, gave the corresponding complex 6 in excellent chemical yield (97.2%). Without any purification the intermediate 6 was cyclized under homogeneous conditions (DMF, NaO-t-Bu) to give the product 7 in high chemical yield (93.1%). Decomposition of prepared 7 afforded the target amino acid 2-aminoindane-2-carboxylic acid (1) in 97.9% yield, along with recovery of ligand 8, which was converted back to the starting glycine complex 2b. Operationally convenient experimental procedures, mild reaction conditions, as well as high chemical and volume yields render the method practical for preparing amino acid 1 and its analogues.