A novel photoarylation of amino acids and peptides is described, which tolerates the presence of water. Irradiation of Boc-protected amino acids in the presence of N-protected 2-azidobenzimidazoles leads to selective arylation of carboxy termini or side chains. The new reaction also works for peptides. Irradiation of the nonapeptide H-SPSYVYHQF-OH also resulted in selective arylation of the tyrosine side chains, as indicated by ESI-MS/MS fragmentation. Chemo- and regioselectivity could add the title reaction to the repertoire of photoaffinity labeling methods.

Irradiation of N-benzylated 2-azidobenzimidazoles at 300 nm in the presence of an excess amount of carboxylic acids results in a novel regioselective synthesis of 2-amino-6-oxybenzimidazoles in isolated yields of 60–70 %. It is also possible to regioselectively introduce 6-bromo, 6-chloro, and 6-triflyloxy groups. Irradiation in dichloromethane in the absence of external nucleophiles revealed that after loss of nitrogen, the benzimidazolylnitrene probably undergoes coarctate ring opening to an N-cyano diaza-o-xylylene intermediate.

A structure–activity relationship study of ring C-functionalized derivatives of the cytotoxic marine natural product(–)-dibromophakellstatin from the sponge Phakellia mauritiana is reported. Functionalization of the pyrrolidine ring was achieved starting from the hydroxy derivative by conversion to the triflate followed by etherification by epimerizing nucleophilic substitution. We identified (12R)-dibromo-12-hydroxyphakellstatin as the most cytotoxic derivative, which exhibited an average IC₅₀ value of 1.4 μM against a panel of twelve human cancer cell lines. However, the 12S diastereomer was inactive. Dehydrophakellstatin was synthesized as the first example of a phakellin skeleton with an unsaturated ring C.

The glucosylated monoterpenoids (–)-rhodioloside A and (–)-rhodioloside D from the roseroot (Rhodiola rosea) have been synthesized for the first time. Glucosylation with tetrapivaloylglucosyl bromide proved superior to the use of tetraacetylglucosyl bromide or glucosyl iodides. Acid-catalyzed cyclization of a homoglycidol-type geraniol derivative afforded the monoterpenoid tetrahydrofuran (+)-sachalinol C from Rhodiola sachalinensis. The absolute configuration of (+)-sachalinol C requires revision. (–)-Sachalinol A and (–)-sachalinol B were also obtained.

As characteristic structural elements of several of the non-monomeric pyrrole-imidazole alkaloids, 1,1-bis(imidazolyl)propenes were assembled in a facile manner by double Grignard reaction of metalated imidazoles with saturated esters, followed by dehydration. The presence of nitrile functions or acryl esters in the electrophile component leads to competing reactions, whereas propargyl esters are tolerated. Introduction of 2-amino groups was possible via the corresponding dimethylsulfamoyl-protected 2-azidoimidazoles, which had to be deprotected prior to hydrogenation. NOESY-based analysis revealed preferred orientation of the imidazole 5-positions towards the propenyl chain.