Improved preparation deoxophylloerythroetioporphyrin (DPEP) and its 15′-methyl derivative from chlorophyll a

Deciphering structure and aggregation in asphaltenes: hypothesis-driven design and development of synthetic model compounds

Asphaltenes comprise the heaviest and least understood fraction of crude petroleum. The asphaltenes are a diverse and complex mixture of organic and organometallic molecules in which most of the molecular constituents are tightly aggregated into more complicated suprastructures. The bulk properties of asphaltenes arise from a broad range of polycyclic aromatics, heteroatoms, and polar functional groups. Despite much analytical effort, the precise molecular architectures of the material remain unresolved. To understand asphaltene characteristics and reactivity, the field has turned to synthetic model compounds that mirror asphaltene structure, aggregation behavior, and thermal chemistry, including the nucleation of coke. Historically, molecular asphaltene modeling was limited to commercial compounds, offering little illumination and few opportunities for hypothesis-driven research. More recently, however, rational molecular design and modern organic synthesis have started to impact this area. This review provides an overview of commercially available model compounds but is principally focused on the design and synthesis of structurally advanced and appropriately functionalized compounds to mimic the physical and chemical behavior of asphaltenes. Efforts to model asphaltene aggregation are briefly discussed, and a prognosis for the field is offered. A referenced tabulation of the synthetic compounds reported to date is provided.

Synthesis, photophysical properties, in vivo photosensitizing efficacy, and human serum albumin binding properties of some novel bacteriochlorins

The synthesis, photophysical characteristics, in vivo photosensitizing efficacy, human serum albumin (HSA) binding properties, and skin phototoxicity of some stable bacteriochlorins were investigated. The novel bacteriochlorins, obtained from chlorophyll-a, have long-wavelength absorptions in the range lambda max = 734-758 nm. Preferential migration of ethyl over methyl substituents among ketobacteriochlorins obtained in the pinacol-pinacolone rearrangements of vic-dihydroxybacteriochlorins was confirmed by NOE studies. The bacteriochlorins show relatively low fluorescence quantum yields. Among all the bacteriochlorins the triplet states were quenched by ground state molecular oxygen in a relatively similar manner, yielding comparable singlet oxygen quantum yields. In preliminary in vivo studies (DBA/2 mice, transplanted with SMT/F tumors), ketobacteriochlorins were found to be more photodynamically active than the related vic-dihydroxy analogues. Replacement of the methyl ester functionalities with di-tert-butylaspartic acids enhanced the in vivo efficacy. Site specific human serum albumin (HSA) binding studies indicated a direct correlation between the ability of the compound to bind to the diazepam binding site (albumin site II) and the in vivo photosensitizing efficacy.