Carbohydrates as chiral intermediates in organic synthesis. Two functionalized chemical precursors comprising eight of the ten chiral centers of erythronolide A

1977 ◽  
Vol 55 (6) ◽  
pp. 1111-1113 ◽  
Author(s):  
Stephen Hanessian ◽  
Georges Rancourt
Keyword(s):  
Organic Synthesis ◽  
Chiral Intermediates ◽  
Chiral Centers ◽  
Branched Chain

Two appropriately functionalized branched-chain sugars have been synthesized as potentially useful chemical precursors to erythronolide A, encompassing its C-1–C-6 and C-9–C-15 segments respectively.

Self-Assembly of a Chiral Cubic Three-Connected Net from the High Symmetry Molecules C60 and SnI4

2020 ◽  
Author(s):  
Daniel B. Straus ◽  
Robert J. Cava
Keyword(s):  
Organic Synthesis ◽  
Self Assembly ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
High Symmetry ◽  
Molecular Chirality ◽  
Chiral Materials ◽  
Self Assembled ◽  
Chiral Centers

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with chiral centers. Less commonly, achiral molecules can self-assemble into chiral materials, despite the absence of intrinsic molecular chirality. Here, we demonstrate the assembly of high-symmetry molecules into a chiral van der Waals structure by synthesizing crystals of C<sub>60</sub>(SnI<sub>4</sub>)<sub>2</sub> from icosahedral buckminsterfullerene (C<sub>60</sub>) and tetrahedral SnI4 molecules through spontaneous self-assembly. The SnI<sub>4</sub> tetrahedra template the Sn atoms into a chiral cubic three-connected net of the SrSi<sub>2</sub> type that is held together by van der Waals forces. Our results represent the remarkable emergence of a self-assembled chiral material from two of the most highly symmetric molecules, demonstrating that almost any molecular, nanocrystalline, or engineered precursor can be considered when designing chiral assemblies.

PLAYING IN THE FRONTIERS OF THE WOODWARD-HOFFMANN RULES

2021 ◽  
Author(s):  
Carlos Silva López ◽  
Keyword(s):  
Organic Synthesis ◽  
Microscopic Level ◽  
Pericyclic Reactions ◽  
Computational Tools ◽  
New Era ◽  
Eye Opening ◽  
Degree Of Control ◽  
Chiral Centers ◽  
High Degree

Pericyclic reactions are known for their exquisite selectivity and, in many cases, the formation of multiple chiral centers with a high degree of control. With the advent of accurate computational tools, this control was translated into predictability, and the design and exploitation of this set of reactions opened a new era in organic synthesis. Suddenly, highly complex and profusely decorated polycyclic structures were accessible in relatively short reaction sequences. Out interest in exploring the limits of application of the rules that govern these reactions with ironfist led us to discover a range of eye opening post-transitional effects that are key to ultimately understand reactivity at a microscopic level.

scholarly journals A Chiral Van Der Waals Material Self-Assembled from the High Symmetry Molecules C60 and SnI4

2020 ◽  
Author(s):  
Daniel B. Straus ◽  
Robert J. Cava
Keyword(s):  
Organic Synthesis ◽  
Self Assembly ◽  
Van Der Waals ◽  
The Self ◽  
High Symmetry ◽  
Molecular Chirality ◽  
Molecular Precursor ◽  
Chiral Materials ◽  
Self Assembled ◽  
Chiral Centers

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with chiral centers. Less commonly, achiral molecules can self-assemble into chiral materials, despite the absence of intrinsic molecular chirality. Here, we demonstrate the assembly of high-symmetry molecules into a chiral van der Waals structure by synthesizing crystals of C<sub>60</sub>(SnI<sub>4</sub>)<sub>2</sub> from icosahedral buckminsterfullerene (C<sub>60</sub>) and tetrahedral SnI<sub>4</sub> molecules through spontaneous self-assembly. Our results represent the remarkable emergence of chirality from the self-assembly of two of the most highly symmetric molecules, demonstrating that almost any molecular precursor can be considered when designing chiral assemblies.

Sialyl aldolase in organic synthesis: from the trout egg acid 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) to branched-chain higher ketoses as possible new chirons.

Tetrahedron ◽  
1990 ◽  
Vol 46 (1) ◽  
pp. 201-214 ◽  
Author(s):  
Claudine Augé ◽  
Christine Gautheron ◽  
Serge David ◽  
Annie Malleron ◽  
Bertrand Cavayé ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Nonulosonic Acid ◽  
Branched Chain

Self-Assembly of a Chiral Cubic Three-Connected Net from the High Symmetry Molecules C60 and SnI4

2020 ◽  
Author(s):  
Daniel B. Straus ◽  
Robert J. Cava
Keyword(s):  
Organic Synthesis ◽  
Self Assembly ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
High Symmetry ◽  
Molecular Chirality ◽  
Chiral Materials ◽  
Self Assembled ◽  
Chiral Centers

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with chiral centers. Less commonly, achiral molecules can self-assemble into chiral materials, despite the absence of intrinsic molecular chirality. Here, we demonstrate the assembly of high-symmetry molecules into a chiral van der Waals structure by synthesizing crystals of C<sub>60</sub>(SnI<sub>4</sub>)<sub>2</sub> from icosahedral buckminsterfullerene (C<sub>60</sub>) and tetrahedral SnI4 molecules through spontaneous self-assembly. The SnI<sub>4</sub> tetrahedra template the Sn atoms into a chiral cubic three-connected net of the SrSi<sub>2</sub> type that is held together by van der Waals forces. Our results represent the remarkable emergence of a self-assembled chiral material from two of the most highly symmetric molecules, demonstrating that almost any molecular, nanocrystalline, or engineered precursor can be considered when designing chiral assemblies.

scholarly journals A Novel Dual Organocatalyst for the Asymmetric Pinder Reaction and a Mechanistic Proposal Consistent with the Isoinversion Effect Thereof

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6398
Author(s):  
Fotini Moschona ◽  
Athena Vagena ◽  
Veroniki P. Vidali ◽  
Gerasimos Rassias
Keyword(s):  
Natural Products ◽  
Transition State ◽  
Organic Synthesis ◽  
Lewis Acid ◽  
Medicinal Chemistry ◽  
Aromatic Aldehydes ◽  
Bioactive Molecules ◽  
Knoevenagel Reaction ◽  
Chiral Centers

In general, the Pinder reaction concerns the reaction between an enolisable anhydride and an aldehyde proceeding initially through a Knoevenagel reaction followed by the ring closing process generating lactones with at least two chiral centers. These scaffolds are frequently present in natural products and synthetic bioactive molecules, hence it has attracted intense interest in organic synthesis and medicinal chemistry, particularly with respect to controlling the diastereo- and enantioselectivity. To the best of our knowledge, there has been only one attempt prior to this work towards the development of a catalytic enantioselective Pinder reaction. In our approach, we designed, synthesized, and tested dual chiral organocatalysts by combining BIMAH amines, (2-(α-(alkyl)methanamine)-1H-benzimidazoles, and a Lewis acid motif, such as squaramides, ureas and thioureas. The optimum catalyst was the derivative of isopropyl BIMAH bearing a bis(3,5-trifluoromethyl) thiourea, which afforded the Pinder products from various aromatic aldehydes with diastereomeric ratio >98:2 and enatioselectivity up to 92 ee%. Interestingly, the enantioselectivity of this catalyzed process is increased at higher concentrations and exhibits an isoinversion effect, namely an inverted "U" shaped dependency with respect to the temperature. Mechanistically, these features, point to a transition state involving an entropy-favored heterodimer interaction between a catalyst/anhydride and a catalyst/aldehyde complex when all other processes leading to this are much faster in comparison above the isoinversion temperature.

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