Exploratory Studies on the Synthesis of the Unusual Diterpenoid Tropone Harringtonolide.

1999 ◽  
Vol 52 (11) ◽  
pp. 1093 ◽  
Author(s):  
Daniel H. Rogers ◽  
Barbara Frey ◽  
Francis S. Roden ◽  
Friedrich-Wilhelm Russkamp ◽  
Anthony C. Willis ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Transition Metal ◽  
Total Synthesis ◽  
Aldol Reaction ◽  
Ring System ◽  
Aryl Ring ◽  
Mercuric Nitrate ◽  
Catalysed Reaction

Various approaches to the total synthesis of the unusual diterpenoid tropone (2), discovered in the yew species Cephalotaxus harringtonia and C. hainanensis, are described. The rhodium-catalysed intramolecular cyclopropanation reaction of an aryl ring by means of the transition metal catalysed reaction of a diazoacetyl function was used to assemble the 5/7 ring system and to provide a cycloheptatrienyl precursor to the tropone moiety, e.g.(28)→(29) and (38) →(39). In the most promising approach, the carbocyclic system was assembled by means of the aldol reaction (42) →(43) with the newly formed α-hydroxyl being employed subsequently in the formation of the δ-lactone function of (44). The tropone ring may be formed from the methoxycycloheptatriene moiety simply by treatment with mercuric nitrate. Tropone (45) was formed from (44) in this way, but attempts to convert it into harringtonolide by means of transannular oxidation based on the 4-hypoiodite failed. The crystal structure of an intermediate is reported.

Total Synthesis of the Pentacyclic Diterpenoid Tropone Hainanolidol

2000 ◽  
Vol 53 (10) ◽  
pp. 819 ◽  
Author(s):  
Barbara Frey ◽  
Adam P. Wells ◽  
Frances Roden ◽  
Ty Duong Au ◽  
David C. Hockless ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Oxidation Process ◽  
Aldol Reaction ◽  
Ring System ◽  
Protecting Group ◽  
X Ray ◽  
Catalysed Reaction ◽  
Process Methodology ◽  
The Stability ◽  
Carbonyl Function

The total synthesis of the unusual diterpenoid tropone, hainanolidol (1), discovered in the bark of the yew species, Cephalotaxus hainanensis, has been completed in 26 steps from 3,5-dimethylanisole. The intramolecular cyclopropanation reaction of the aryl ring in (30) by means of the rhodium mandelate-catalysed reaction of the diazoacetyl function was used to assemble the 5/7 ring system of (31), at the same time elaborating a cycloheptatriene moiety that could be transformed subsequently to the tropone functionality in the target molecule. While removing the acetal protecting group from (31) an unexpected Mukaiyama–type aldol process was induced by ZnBr2, affording (32), the structure of which was determined by X-ray analysis. With greater care, the aldehyde (33) could be obtained and the desired carbocyclic ring system completed by means of a base-catalysed aldol reaction with the newly formed hydroxyl being employed subsequently in the formation of the σ-lactone function in (35). Desilylation, reduction of the C-10 carbonyl function and brief exposure to acid finally afforded (1). This last step took advantage of the stability of the tropylium ion (40) to provide a ‘thermodynamic sink’ for the reaction outcome. The synthesis of (1) also constitutes a formal synthesis of the troponoid ether, harringtonolide (2), since this compound had been obtained previously from (1) by means of a transannular oxidation process. Methodology for the assembly of the tropone moiety in (1) and (2) was modelled on the simpler bi- and tricyclic systems, (13) and (22), respectively.

Concise Total Synthesis of Curvulone B

Synlett ◽  
2020 ◽  
Author(s):  
Debendra K. Mohapatra ◽  
Shivalal Banoth ◽  
Utkal Mani Choudhury ◽  
Kanakaraju Marumudi ◽  
Ajit C. Kunwar
Keyword(s):  
Total Synthesis ◽  
Stereoselective Synthesis ◽  
Ring System ◽  
Bond Forming ◽  
Cross Metathesis ◽  
Bond Forming Reactions ◽  
Key Steps

AbstractA concise and convergent stereoselective synthesis of curvulone B is described. The synthesis utilized a tandem isomerization followed by C–O and C–C bond-forming reactions following Mukaiyama-type aldol conditions for the construction of the trans-2,6-disubstituted dihydropyran ring system as the key steps. Other important features of this synthesis are a cross-metathesis, epimerization, and Friedel–Crafts acylation.

ChemInform Abstract: TOTAL SYNTHESIS OF THE 6-SILASTEROID RING SYSTEM

1975 ◽  
Vol 6 (52) ◽  
pp. no-no
Author(s):  
S. BARCZA ◽  
C. W. HOFFMAN
Keyword(s):  
Total Synthesis ◽  
Ring System

scholarly journals Short, enantioselective, gram-scale synthesis of (−)-zephyranthine

2021 ◽  
Author(s):  
Yuxiang Zhao ◽  
Yanren Zhu ◽  
Guolan Ma ◽  
Qi Wei ◽  
Shaoxiong Yang ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Functional Group ◽  
Ring System ◽  
System Construction ◽  
Synthesis Design

A reasonable synthesis design by strategically integrating functional group manipulation into the ring system construction resulted in a short, enantioselective, gram-scale total synthesis of (−)-zephyranthine.

scholarly journals Crystal structure of 5,10,15-triphenyl-20-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)porphyrin

2014 ◽  
Vol 70 (10) ◽  
pp. o1085-o1086
Author(s):  
Mathias O. Senge ◽  
Hans-Georg Eckhardt
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Central Region ◽  
Title Compound ◽  
Ring System ◽  
Compound C ◽  
Porphyrin Macrocycle ◽  
Phenyl Rings ◽  
Supramolecular Chains

In the title compound, C44H37BN4O2, the dihedral angle between the plane of the porphyrin macrocycle ring system [r.m.s. deviation = 0.159 (1) Å] and those of three phenyl rings are 66.11 (4), 74.75 (4) and 57.00 (4)°. The conformational distortion is characterized by a mixture of ruffled, saddle and in-plane distortion modes. In the crystal, the porphyrin molecules are linked by C—H...π interactions into supramolecular chains running along thea-axis direction. A pair of bifurcated N—H...(N,N) hydrogen bonds occur across the central region of the macrocycle.

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