ABSTRACT
An efficient approach to 2-quinolinone derivatives 1 via Diels-Alder cyclization of exo-diene lactams 5 and dienophiles is reported.
Subject(s)
Lactams/chemistry , Quinolones/chemical synthesis , Catalysis , Combinatorial Chemistry Techniques , Cyclization , Molecular Structure , Quinolones/chemistryABSTRACT
[reaction: see text] The reaction of alpha-sulfonyl acetamide 1 with various cyclic unsaturated esters 2 to fused bicyclic glutarimides is reported. Syntheses of (+/-)-alloyohimbane (4) and louisianin D (5) have been accomplished.
Subject(s)
Allyl Compounds/chemical synthesis , Heterocyclic Compounds, 4 or More Rings/chemical synthesis , Piperidones/chemical synthesis , Pyridines/chemical synthesis , Allyl Compounds/chemistry , Catalysis , Crystallography, X-Ray , Esters , Heterocyclic Compounds, 4 or More Rings/chemistry , Molecular Conformation , Molecular Structure , Piperidones/chemistry , Pyridines/chemistry , StereoisomerismABSTRACT
We have provided a model to interpret the non-quadratic-intensity dependence behavior commonly observed in the two-photon fluorescence (TPF) experiment excited with high laser intensity. The model also provides one with a different technique to measure the two-photon absorption cross section of an organic chromophore in solution. In contrast to the commonly used low intensity technique that depends on the quadratic-intensity law, the present technique is based on the non-quadratic-intensity dependence of two-photon fluorescence. Auxiliary data such as two-photon quantum efficiency and fluorescence collection efficiency, essential in the low intensity method, are not required in the present technique. TPF measurements of Rhodamine B in methanol are carried out to demonstrate the validity of the present method. The method is used to determine the two-photon absorption cross section of a new chromophore attached with tricyano-derivatized furan as the electron acceptor. The two-photon absorption cross section measured using this method is also compared with that using a conventional transmission technique.
ABSTRACT
A convenient method for the preparation of 5-methoxy-6-substituted-3-sulfonyl-delta-enlactams via regioselective nucleophilic addition to 5-methoxy-3-sulfonyl glutarimide is described. Formal syntheses of L-733,060, CP-99,994, and cassine are also reported.
Subject(s)
Lactams/chemical synthesis , Piperidines/chemical synthesis , Piperidones/chemistry , Molecular Structure , StereoisomerismABSTRACT
[reaction: see text] Base-induced coupling/cyclization reactions of alpha-sulfonylacetamide with various ethyl (Z)-2-bromo-2-propenoates have been carried out. The polysubstituted pyroglutamate carbon skeleton, with three contiguous asymmetric centers, was built up in one step. A ring-closure mechanism is proposed for the reactions.
ABSTRACT
Sodium borohydride regioselectively reduced various 3-sulfonyl glutarimides 1 to hydroxy piperidones 2, which were further dehydrated to 3,4-dihydro-5-sulfonylpyridin-2-ones 3 in the presence of boron trifluoride. Formal synthesis of 8a-epi-dendroprimine (4) possessing an indolizidine ring system has been accomplished via intramolecular radical cyclization of cyclic vinyl sulfone 5.
ABSTRACT
A total synthesis of (+/-)-sarracenin (1) is described. The key steps include (1) regioselective ring expansion of 7 to bicyclo[3.2.1]ketone6 and (2) ring opening of tricyclic ketone 5 to ester 4.
