Argentation chromatography is used to increase the selectivity of the chromatographic process, chiefly in the resolution of complex mixtures of nonpolar substances. Although efficient, this technique generates residues containing heavy metal which makes its discarding through common procedures impracticable. In the present work a simple method for recycling of silica, and also silver, from argentation chromatography is described. This procedure uses initially a treatment of H2O2/HNO3, with subsequent treatment with H2O2/H2SO4 , allowing an efficient recycling of both components. This methodology is simple, costless, removes impurities efficiently, and does not modify retention parameters nor specific surface in a significant way.

A synthesis of artificial sweetener dulcin starting from nitrobenzene was elaborated for undergraduate organic laboratory course. Paracetamol and phenacetin, both physiologically active analgesic compounds, were also prepared as intermediates. Besides a large scope of discussion subjects related with organic synthesis, interesting lectures about analgesics and sweeteners may also be performed in this project. The advantage of this project is the adaptability according to the conditions offered by the course, i.e., convenience and/or availability of time and reagents.

Da casca do tronco de Hymenaea courbaril var. altissima (Ducke) foi isolado um novo ent-clerodano na forma de éster metílico, após esterificação com diazometano, o (-)-(5R,8S,9S,10R)-clerod-3-en-15-oato de metila. Foram isolados também dois ent-labdanos conhecidos: o (-)-copalato de metila e (-)-eperuato de metila. Do extrato AcOEt do epicarpo foi isolado, após esterificação com diazometano, o (-)-zanzibarato de metila. As estruturas dos compostos foram elucidadas com base na análise de dados espectroscópicos.

A new ent-clerodane and two known ent-labdanes were isolated from the barks of Hymenaea courbaril var. altissima (Ducke). The new diterpene was identified, after esterification with diazomethane, as methyl (-)-(5R,8S,9S,10R)-clerod-3-en-15-oate and known diterpenes were identified as methyl (-)-copalate and methyl (-)-eperuate. From the EtOAc extract of seed pods a known methyl (-)-zanzibarate was isolated. The structures of isolated compounds were elucidated based on spectroscopic studies.

Reação do alilsilano quiral 3 com alfa-metil-beta-siloxi-aldeídos fornece os produtos correspondentes com estereoquímica relativa 1,4-syn com boa diastereosseletividade, independente da estereoquímica absoluta dos aldeídos. As melhores seletividades são observadas quando ocorre transmetalação do alilsilano 3 usando SnCl4 em CH2Cl2, a -78 °C, antes da adição dos aldeídos.

Chiral allylsilane 3 reacted with chiral alpha-methyl-beta-siloxy-aldehydes to afford the corresponding 1,4-syn-products with good diastereoselectivities independent of the absolute stereochemistry of these aldehydes. The best selectivities are observed when the reactions are carried out by transmetallation of the allylsilane 3 using Tin (IV) Chloride in CH2Cl2, at -78 °C, before addition of the aldehydes.