PubMed · 5399804
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T Nguyen-Dang, M Mayer. 1969. [Filter for preparative chromatography].. https://pubmed.ncbi.nlm.nih.gov/5399804/
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Treatment of 9-(2,3,5-tri-O-acetyl-beta-d-ribofuranosyl)-2-amino-6-chloropurine (1) with TMS-Cl and benzyltriethylammonium nitrite (BTEA-NO2) in dichloromethane gave the crystalline 2,6-dichloropurine nucleoside 2, and acetyl chloride/BTEA-NO2 was equally effective ( approximately 85%, without chromatography). TMS-Br/tert-butyl nitrite/dibromomethane gave crystalline 2-bromo-6-chloro analogue 3 (85%). (Chloro or bromo)-dediazoniation of 3',5'-di-O-acetyl-2'-deoxyadenosine (4) gave the 6-[chloro (5, 63%) or bromo (6, 80%)]purine deoxynucleosides, and 2',3',5'-tri-O-acetyladenosine (8) was converted into the 6-chloropurine nucleoside 9 (71%).
A stereocontrolled total synthesis of both the (+)- and (-)-epolactaene ((+)- and (-)-1) enantiomers from tetrahydropyran-2-ol is described. The following reactions in this synthesis are particularly noteworthy: (1) the stereoselective construction of the conjugated (E,E,E)-triene by a combination of kinetic deprotonation and thermodynamic equilibration, (2) the E-selective Knoevenagel condensation of beta-ketonitrile 33 with a chiral 2-alkoxyaldehyde, (3) a diastereoselective epoxidation achieved using a bulky nucleophile (TrOOLi) and an appropriate protecting group, (4) the mild hydrolysis of an alpha-epoxy nitrile by silica gel on TLC facilitated by hydroxyl-mediated, intramolecular assistance.
The Soxflo technique was evaluated for the rapid extraction of plant materials (<90 min) at room temperature. Qualitatively similar chromatograms were obtained by gas chromatography and thin layer chromatography (TLC) with Soxflo (SoF) and Soxhlet (SoL) extracts. Sequential solvent extractions by SoF gave slightly higher yields (132%) of five major sesquiterpenoids. TLC revealed that SoF extractions at room temperature were more selective as extracts contained compounds with a narrower range of R(f)() values. This means that the SoF technique offers the potential for one-step extractions and partial fractionation. This study also showed that there were large differences in the volatile composition of dried and fresh Piper fruits: dried fruits had predominantly sesquiterpenoids while fresh fruits had considerable quantities of both mono- and sesquiterpenoids. This is the first report of alpha-guaiene and alpha- and beta-selinene in Piper guineense fruits. It is suggested that the SoF technique can be useful for the screening of large numbers of plants for phytochemicals or for the preparation of plant extracts for subsequent bioassay studies.