Crystal structure of LepI, a multifunctional SAM-dependent enzyme which catalyzes pericyclic reactions in leporin biosynthesis

2019 ◽  
Vol 17 (8) ◽  
pp. 2070-2076 ◽  
Author(s):  
Zhenying Chang ◽  
Tamar Ansbacher ◽  
Lilan Zhang ◽  
Yong Yang ◽  
Tzu-Ping Ko ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Claisen Rearrangement ◽  
Alder Reaction ◽  
Diels Alder ◽  
Pericyclic Reactions ◽  
Diels Alder Reaction

Crystal structure of LepI, a SAM-dependent enzyme which can catalyze seteroselective dehydration, Diels–Alder reaction, and retro-Claisen rearrangement.

The Syntheses and Crystal-Structures of Decahydro-5,14:6,13:7,12-Trimethanopentacene and Decahydro-5,14-7,12-Dimethanopentacene: Two Useful Molecules for Investigating Laticyclic Hyperconjugation

1986 ◽  
Vol 39 (10) ◽  
pp. 1587 ◽  
Author(s):  
DC Craig ◽  
MN Paddonrow ◽  
HK Patney
Keyword(s):  
Crystal Structure ◽  
Ab Initio Calculations ◽  
Crystal Structures ◽  
Reductive Dechlorination ◽  
Photoelectron Spectrum ◽  
Alder Reaction ◽  
Diels Alder ◽  
Basis Set ◽  
Orbital Interactions ◽  
Diels Alder Reaction

The syntheses of decahydro-5,14:6,13:7,12-trimethanopentacene and decahydro-5,14:7,12-dimethanopentacene are described (see Schemes 1 and 2 respectively). Diels -Alder reaction of diene (10) with two equivalents of tetrachlorothiophen 1,1-dioxide (11) gave the adduct (12), which was aromatized to (13) through treatment with base. Reductive dechlorination (Na/ PriOH ) of (13) gave (6). A similar set of reactions performed on (17), itself prepared from cyclohexa-1,4-diene and two equivalents of hexachlorocyclopentadiene (15), gave (7). The crystal structures of (6) and (7) were determined. An interesting feature of the structure of (7) is the slight endo pyramidalization (by c. 3°) of the trigonal carbon atoms C 4a, C 7a, C 11a and C 14a. Model ab initio calculations (STO-3G basis set) on complexes (27) and (28), whose geometries were culled from the crystal structure of (6), indicate that significant laticyclic hyperconjugative interactions (c. 0.3 eV ) are mainly responsible for causing the observed splitting between the πs+πs and πs-πs levels in the photoelectron spectrum of (6). Orbital interactions through the pair of six connecting sigma bonds (OIT-6-B) in (6) have a negligible effect (c. 0.08 eV ) on these levels. In agreement with prediction, laticyclic hyperconjugation does not affect the πa+πa and πa-πa levels.

Ring-Closing Metathesis Approach to Cage Propellanes Containing Oxepane and Tetrahydrofuran Hybrid System

Synthesis ◽  
2017 ◽  
Vol 49 (24) ◽  
pp. 5339-5350 ◽  
Author(s):  
Sambasivarao Kotha ◽  
Subba Cheekatla ◽  
Darshan Mhatre
Keyword(s):  
Claisen Rearrangement ◽  
Alder Reaction ◽  
Diels Alder ◽  
Ring Closing Metathesis ◽  
Cage Compounds ◽  
Transannular Cyclization ◽  
Diels Alder Reaction ◽  
Grignard Addition ◽  
Key Steps ◽  
First Time

The preparation of a variety of structurally interesting oxygenated cage compounds involving atom-economic processes such as Claisen rearrangement, Diels–Alder reaction, [2+2] photocycloaddition, and ring-closing metathesis (RCM) as key steps is reported. For the first time, oxepane ring system is introduced in cage framework using olefin metathesis as a key step. These cage systems assembled here are difficult to prepare by traditional methods. The synthetic sequence described here opens up new routes to higher order polycycles containing heteroatoms without the involvement of protecting groups. Transannular cyclization observed during Grignard addition and the RCM protocol used here may be applicable to generate unknown oxygenated cage systems.

scholarly journals Crystal structure of (1S,2R,6R,7R,8S,12S)-4,10,17-triphenyl-15-thia-4,10-diazapentacyclo[5.5.5.01,16.02,6.08,12]heptadeca-13,16-diene-3,5,9,11-tetronep-xylene hemisolvate

2014 ◽  
Vol 70 (12) ◽  
pp. 550-554 ◽  
Author(s):  
Wayland E. Noland ◽  
Neil J. Kroll ◽  
Matthew P. Huisenga ◽  
Ruixian A. Yue ◽  
Simon B. Lang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Alder Reaction ◽  
Major Product ◽  
Diels Alder ◽  
Inversion Center ◽  
Compound C ◽  
Diels Alder Reaction

The title tetrone compound, C32H22N2O4S· 0.5C8H10, is the major product (50% yield) of an attempted Diels–Alder reaction of 2-(α-styryl)thiophene withN-phenylmaleimide (2 equivalents) in toluene. Recrystallization of the resulting powder fromp-xylene gave the title hemisolvate; thep-xylene molecule is located about an inversion center. In the crystal, the primary tetrone contacts are between a carbonyl O atom and the four flagpole H atoms of the bicyclo[2.2.2]octene core, forming chains along [001].

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