ABSTRACT
The first biomimetic homodimerization of oroidin and clathrodin was effected in the presence HMPA and diphosphonate salts, strong guanidinium and amide chelating agents. The intermolecular associations probably interfere with the entropically and kinetically favored intramolecular cyclizations. Use of oroidin·(1)/2HCl salt or clathrodin·(1)/2HCl was indicative in the presence of the ambident nucleophilic and electrophilic tautomers of the 2-aminoimidazolic oroidin and clathrodin precursors. Surprisingly, the homodimerization of oroidin led to the nagelamide D skeleton, while the homodimerization of clathrodin gave the benzene para-symmetrical structure 19. The common process was rationalized from tautomeric precursors I and III.
Subject(s)
Hempa/chemistry , Imidazoles/chemistry , Pyrroles/chemistry , Cyclization , Marine Biology , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular , StereoisomerismABSTRACT
Four new dimeric pyrrole-2-aminoimidazole alkaloids have been isolated from the Pacific marine sponges Agelas cf. mauritiana and Phakellia sp. They include the unusual C2 symmetrical benzosceptrins A (4) and B (5), which each possess a unique benzocyclobutane skeleton and nagelamides S (6) and T (7). Their structures and relative configuration were elucidated from spectroscopic data. Plausible biogenetic paths for these compounds are also proposed in this paper.
Subject(s)
Agelas/chemistry , Alkaloids/isolation & purification , Imidazoles/isolation & purification , Pyrroles/isolation & purification , Alkaloids/chemistry , Animals , Imidazoles/chemistry , Marine Biology , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular , Pacific Ocean , Pyrroles/chemistryABSTRACT
Beta-amino alcohols derived from natural amino acids have been used extensively as a powerful source of chirality. Transformation of the hydroxy group of these beta-amino alcohols into a good leaving group, by using trifluoroacetic anhydride, led to rearranged beta-amino alcohols in good yields and with high enantiomeric excesses. This rearrangement has allowed the transformation of substituted prolinols to substituted 3-hydroxypiperidines and linear beta-amino alcohols, issued from natural amino acids, to rearranged beta-amino alcohols.
Subject(s)
Amino Alcohols/chemistry , Pharmaceutical Preparations/chemical synthesis , Amino Alcohols/chemical synthesis , Catalysis , Pharmaceutical Preparations/chemistry , StereoisomerismABSTRACT
Three new diterpene alkaloids, agelasine J (3), agelasine K (4), and agelasine L (5), were isolated from the marine sponge Agelas cf. mauritiana collected in the Solomon Islands. The structures of these compounds were elucidated by physical data analyses. They displayed in vitro antimalarial activity against Plasmodium falciparum.
Subject(s)
Alkaloids/isolation & purification , Diterpenes/isolation & purification , Alkaloids/chemistry , Alkaloids/pharmacology , Animals , Antimalarials/chemistry , Antimalarials/isolation & purification , Antimalarials/pharmacology , Chromatography, High Pressure Liquid , Diterpenes/chemistry , Diterpenes/pharmacology , Mass Spectrometry , Molecular Structure , Plasmodium falciparum/drug effects , PoriferaABSTRACT
New debromopyrrole-2-aminoimidazolones, debromodispacamide B (1) and debromodispacamide D (2) were isolated from the sponge Agelas mauritiana, collected in the Solomon Islands. A biomimetic one-step reaction from pseudopeptides 5 and 13 in presence of air oxygen and guanidine gave the chiral form of the natural product stereoselectively.
Subject(s)
Agelas/chemistry , Imidazoles/isolation & purification , Pyrroles/chemical synthesis , Pyrroles/isolation & purification , Animals , Imidazoles/chemical synthesis , Imidazoles/chemistry , Marine Biology , Molecular Structure , Proline/chemistry , Pyrroles/chemistry , StereoisomerismABSTRACT
[reaction: see text] N,N-Dialkyl-beta-amino alcohols derived from alpha-amino acids can be rearranged enantiospecifically by using TFAA/Et3N/NaOH to give 1,2-amino alcohols with enantiomeric excess up to 99%.
