scholarly journals Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

2018 ◽  
Vol 14 ◽  
pp. 2949-2955 ◽  
Author(s):  
Pierre-Antoine Nocquet ◽  
Aurélie Macé ◽  
Frédéric Legros ◽  
Jacques Lebreton ◽  
Gilles Dujardin ◽  
...  
Keyword(s):  
Natural Products ◽  
Starting Material ◽  
Vinyl Ethers ◽  
Ring Closing Metathesis

In this paper, a new access to several chiral 3-aminoglycals as potential precursors for glycosylated natural products is reported from a common starting material, (−)-methyl-L-lactate. The stereodivergent strategy is based on the implementation of a ring-closing metathesis of vinyl ethers as key step of reaction sequences developed.

Tandem allylboration-ring-closing metathesis reactions for the preparation of biologically active molecules

2003 ◽  
Vol 75 (9) ◽  
pp. 1263-1275 ◽  
Author(s):  
P. Veeraraghavan Ramachandran ◽  
M. Venkat Ram Reddy ◽  
Herbert C. Brown
Keyword(s):  
Organic Chemistry ◽  
Natural Products ◽  
Asymmetric Synthesis ◽  
Biologically Active ◽  
Cyclic Ethers ◽  
Ring Closing Metathesis ◽  
The Past ◽  
Metathesis Reactions

The development of asymmetric synthesis during the past two decades aided organic chemists considerably in the synthesis of complex natural products. Organoborane chemistry continues to play an important role in asymmetric synthesis. One of the important reactions that has become very common in the arsenal of synthetic chemists is allylboration and related reactions. Another important reaction that has recently attained enormous importance in organic chemistry is the ring-closing metathesis (RCM) reaction. Indeed, a combination of allylboration and RCM reactions provides an excellent route to cyclic ethers, lactones, lactams, etc. Herein, we describe a sequential asymmetric allylboration and RCM reaction protocol that has been utilized for the synthesis of several alpha-pyrone-containing natural products,particularly biologically active molecules.

scholarly journals Synthetic Strategies towards Therapeutically Relevant Tailored Macrocycles

2020 ◽  
pp. 6-20
Author(s):  
Ashu Chaudhary ◽  
Subhash . ◽  
Pinki .
Keyword(s):  
Natural Products ◽  
Transition Metal ◽  
Click Reaction ◽  
Cross Coupling ◽  
Full Scale ◽  
Macrocyclic Compounds ◽  
Ring Closing Metathesis ◽  
Engineered Systems ◽  
Synthetic Approaches

The normally used synthetic approaches toward macrocyclization join full scale lactonization, macrolactamization, transition metal catalysed cross coupling, ring-closing metathesis, and click reaction, among others. Picked continuous examples of macrocyclic synthesis of natural products and druglike macrocycles with noteworthy natural significance are highlighted in each class and outline the general engineered systems for the synthesis of macrocycles. The synthesis of macrocyclic compounds incorporating natural products with differing complexities by ring closing metathesis is depicted. Twelve to huge rings that have been orchestrated in moderate to great yields and the synthesis of larger rings as a part of bi-cyclic or poly-cyclic frameworks are likewise depicted in this review.

Synthetic Approaches for Building Tricyclic Cage-like Motifs Found in Indoxamycins

2020 ◽  
Vol 24 ◽  
Author(s):  
Saqlain Haider ◽  
Ikhlas A. Khan ◽  
Hanfeng Ding ◽  
Amar G. Chittiboyina
Keyword(s):  
Natural Products ◽  
Michael Addition ◽  
Claisen Rearrangement ◽  
Biological Activities ◽  
Cascade Reactions ◽  
Biological Properties ◽  
Starting Material ◽  
Central Core ◽  
Chemical Transformations ◽  
One Pot

Abstract:: Indoxamycins A-F, a novel class of polyketides, were isolated from the saline culture of marine-derived actinomyces by Sato et al. in 2009. Intriguing stereochemical complexity involving tricyclic [5.5.6] cage-like structures with six consecutive chiral centers challenged many organic chemists. Chemical ingenuity, implementation of pioneered reactions along with fine chemical transformations allowed not only the rapid construction of the central core but also allowed minor structural revision and paved the information to delineate the absolute stereostructures of these complex polyketide marine natural products. To achieve the central core structure in indoxamycins A-F, reactions like the Ireland- Claisen rearrangement, an enantioselective 1,6-enyne reductive cyclization, and one-pot cascade reactions of 1,2- addition/oxa-Michael/methylenation were employed. Using the chiral pool approach, the readily available R-carvone was employed as a cost-effective starting material to achieve the concise total syntheses of (-)-indoxamycins A and B, in which Pauson-Khand, Cu-catalyzed Michael addition and tandem retro-oxa-Michael addition/1,2-addition/oxa-Michael addition reactions were employed. The antipodes, (+)-indoxamycins can be easily accessed by simply switching to S-carvone as the starting material. Synthetically prepared indoxamycins A-F are devoid of antiproliferative properties which disagrees with the work reported by Sato and co-workers for (-)-indoxamycins A and F. Nevertheless, ready access to such complex natural products allows probing the untapped potential biological activities of these polyketides including cytotoxicity. A concise overview of interesting, key chemical transformations including named reactions in establishing the architecture of indoxamycins was compiled to inspire organic chemists and help reinvigorate the development of novel strategies for the asymmetric synthesis as well as the development of novel derivatives of indoxamycins with unique physicochemical and biological properties.

Synthesis of Carbocyclic Nucleosides (+)-Neplanocin A, (+)-Aristeromycin and 4'-epi-(+)-Aristeromycin from D-Fructose

2019 ◽  
Vol 16 (9) ◽  
pp. 750-758
Author(s):  
Perali R. Sridhar ◽  
Vennam D.K. Reddy ◽  
Mandava Suresh ◽  
Nadiveedhi M. Reddy ◽  
K. Shiva Kumar
Keyword(s):  
Total Synthesis ◽  
Allylic Alcohol ◽  
Starting Material ◽  
Carbocyclic Nucleosides ◽  
Ring Closing Metathesis ◽  
Neplanocin A ◽  
Oxidative Rearrangement ◽  
Key Steps

D-Fructose is used as the chiral pool starting material for the stereoselective total synthesis of (+)-neplanocin A. Zinc mediated fragmentation, ring-closing metathesis and oxidative rearrangement of cyclic tertiary allylic alcohol are used as the key steps in achieving the synthesis of key carbocylic intermediate. Further, stereoselective total synthesis of 4'-epi-(+)-aristeromycin and the conversion of (+)-neplanocin A to a mixture of (+)-aristeromycin and 4'-epi-(+)-aristeromycin are described.

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