Asymmetric syntheses of both enantiomerically pure (+) and (-) 5-oxo-endo-tricyclo [5.2.1.0.^(2,6)] deca-3, 8-diene 1 was described. The key step is the use of enzyme-catalyzed hydrolysis of meso-diacetate 5.
Swerilactones H–K(1–4)as four unprecedented secoiridoid trimers represent a new type of natural product,which has attracted much interest of natural chemists due to their novel skeletons and promising bioactivity.In...Swerilactones H–K(1–4)as four unprecedented secoiridoid trimers represent a new type of natural product,which has attracted much interest of natural chemists due to their novel skeletons and promising bioactivity.In order to well understand their MS fragmentation behaviors,they were investigated by electrospray ionization ion-trap time-of-flight multistage product ion mass spectrometry(ESI-IT-TOF-MSn)for the first time.The protonated molecules([M?H]?)of swerilactones J and K,and deprotonated molecules([M-H]-)of swerilactones H,J and K were readily observed in the conventional single-stage mass spectra(MS);however only the[M?Cl]-ion for swerilactone I was obtained in negative mode.Based on the MSn study,the fragmentation pathways of swerilactones H and I in negative mode,and swerilactones J and K in both positive and negative modes were proposed.The neutral losses of H_(2)O,CO,CO_(2)and C_(2)H_(4)O moieties are the particular elimination from the precursor ions due to the presence of hydroxyl,d-lactone and 1-O-ethyl moieties in their structures,of which the retro-Diels–Alder cleavage was the most particular dissociation.The fragment ions at m/z 341 and 291 in negative mode can be considered as the diagnostic ions for secoiridoid trimers.This investigation will provide valuable information for their fast characterization from complicated natural mixtures and extensive understanding their structural architectures.展开更多
During the course of our program in the synthesis of natural products by retroDiels-Alder reaction using a rigid molecule tricyclo-[5.2.1.0]-deca-4,8-dien-3-one（1） as the starting material, it was observed that aldo...During the course of our program in the synthesis of natural products by retroDiels-Alder reaction using a rigid molecule tricyclo-[5.2.1.0]-deca-4,8-dien-3-one（1） as the starting material, it was observed that aldol condensation of compound （2）展开更多
To study the intramolecular Diels-Alder cycloadditon of 2H-chromen-2-one as a diene, a series of chiral N-allyl-N-benzylamides that contain a 2H-chrornen-2-one moiety were designed for the synthesis of benzo[f]isoindo...To study the intramolecular Diels-Alder cycloadditon of 2H-chromen-2-one as a diene, a series of chiral N-allyl-N-benzylamides that contain a 2H-chrornen-2-one moiety were designed for the synthesis of benzo[f]isoindol-1-ones via an intrarnolecular Diels-Alder and a subsequent retro-Diels-Alder cycloaddition with the expulsion of CO2. Both the yield （80%-89%） and absolute stereocontrol of the tandem reaction were high when an electron-withdrawing group was attached to the dienophile. The double bond in the styrene substructure remained in the products could be further derivatized by dihydroxylation.展开更多
文摘Asymmetric syntheses of both enantiomerically pure (+) and (-) 5-oxo-endo-tricyclo [5.2.1.0.^(2,6)] deca-3, 8-diene 1 was described. The key step is the use of enzyme-catalyzed hydrolysis of meso-diacetate 5.
文摘Swerilactones H–K(1–4)as four unprecedented secoiridoid trimers represent a new type of natural product,which has attracted much interest of natural chemists due to their novel skeletons and promising bioactivity.In order to well understand their MS fragmentation behaviors,they were investigated by electrospray ionization ion-trap time-of-flight multistage product ion mass spectrometry(ESI-IT-TOF-MSn)for the first time.The protonated molecules([M?H]?)of swerilactones J and K,and deprotonated molecules([M-H]-)of swerilactones H,J and K were readily observed in the conventional single-stage mass spectra(MS);however only the[M?Cl]-ion for swerilactone I was obtained in negative mode.Based on the MSn study,the fragmentation pathways of swerilactones H and I in negative mode,and swerilactones J and K in both positive and negative modes were proposed.The neutral losses of H_(2)O,CO,CO_(2)and C_(2)H_(4)O moieties are the particular elimination from the precursor ions due to the presence of hydroxyl,d-lactone and 1-O-ethyl moieties in their structures,of which the retro-Diels–Alder cleavage was the most particular dissociation.The fragment ions at m/z 341 and 291 in negative mode can be considered as the diagnostic ions for secoiridoid trimers.This investigation will provide valuable information for their fast characterization from complicated natural mixtures and extensive understanding their structural architectures.
基金supported by the national Natural Science Foundation of China.
文摘During the course of our program in the synthesis of natural products by retroDiels-Alder reaction using a rigid molecule tricyclo-[5.2.1.0]-deca-4,8-dien-3-one（1） as the starting material, it was observed that aldol condensation of compound （2）
基金supported by the research grant from the National Natural Science Foundation of China (No. 21172191)
文摘To study the intramolecular Diels-Alder cycloadditon of 2H-chromen-2-one as a diene, a series of chiral N-allyl-N-benzylamides that contain a 2H-chrornen-2-one moiety were designed for the synthesis of benzo[f]isoindol-1-ones via an intrarnolecular Diels-Alder and a subsequent retro-Diels-Alder cycloaddition with the expulsion of CO2. Both the yield （80%-89%） and absolute stereocontrol of the tandem reaction were high when an electron-withdrawing group was attached to the dienophile. The double bond in the styrene substructure remained in the products could be further derivatized by dihydroxylation.
