Total Synthesis of Cytosporone B

The total synthesis of Cytosporone B, a naturally occurring agonist for Nur77, has been accomplished. The key steps are the sequential Grignard reaction and Lemieux‐van Rudloff oxidation followed by a deprotection of the methyl aromatic ether to phenol and subsequent Friedel‐Crafts acylation.     

Advances in the First Total Synthesis of Natural Flavonoids

Flavonoids, composed of a C₆-C₃-C₆ backbone, are a kind of secondary metabolites of natural medicine, which widely exist in the higher plant. They have received extensive attention from all over the world and obtained rapid development owing to widespread distribution, structural complexity, active diversity, and molecular plasticity. Total synthesis of natural products is not only one of the most driving forces in organic chemistry but also the embodiment of the development level of organic synthesis chemistry. Total synthesis research possesses not only important theoretical significance to the development of organic chemistry but also potential marketing prospects to clinical medicine and significant practical value to the development of natural medicine. Flavonoids contain flavan, chalcone, flavone, biflavone, isoflavone, xanthone, pterocarpin, homoisoflavone, flavonol, favonolignan, and some other main structure types. This article summarizes the latest research on first total synthesis, including the plant sources and biological activities, of these main structure types, so as to provide some reference for both the research of first total synthesis of natural flavonoids and the development and utilization of their medicinal value.     

Total Synthesis of Terpioside B

The first total synthesis of terpioside B ( 1 ) has been accomplished. Key steps include the stereoselective installments of a set of challenging 1,2-cis-glycosidic linkages. Thus, α(1,4)-linked d -galactoside was effectively constructed from a 1,2-anhydrogalactose donor and an unprotected 1,6-anhydrogalactose acceptor by using a boron-mediated aglycon delivery (BMAD) method. In addition, α-l -fucofuranosides were stereoselectively and simultaneously constructed by remote group-assisted 1,2-cis-α-stereoselective glycosylations.     

Novel Total Synthesis of Mansouramycin B

A novel total synthesis of Mansouramycin B ( 1 ) was performed via 10 steps in 28% overall yield starting from the readily available and cheap salicylaldehyde. Two key steps of this total synthesis are noteworthy. The first one is base‐promoted one‐pot aerobic aromatization of N‐tosyltetrahydroisoquinoline 6 , the second one is oxidation of 5‐hydroxy‐3‐methyl‐isoquinoline 8 with iodobenzene diacetate [PhI(OAc)₂].     

Total Synthesis of Secobatzelline B

A concise and efficient total synthesis of Secobatzelline B is reported. The synthesis involves eight steps starting from known 4,6,7‐trimethoxyindole. Synthetic tactics involve a one‐step reduction of an indole‐3‐glyoxalic ester using LiAlH₄, resulting in complete reduction of the ester group and a partial reduction of the vinylogous amide carbonyl group. Synthesis also involves the use of a mixture of NaCl and oxone as a new reagent for regioselective chlorination of an indoloquinone derivative.     

The First Total Synthesis of Triprenylquinone and Hydroquinones

Marine natural products have received much attention for their attractive structural features and biological activities1. Since the isolation of the moritoside, about 10 related triprenylquinones and hydroquinones were isolated. Some of these natural products exhibit interesting biological effects including inhibit cell division of fertilized starfish eggs2 and anti-HIV3. Triprenylquinone and hydroquinones 1, 2 and 3 were recently isolated from endemic nudibranch Leminda millecra collected i…     

天然产物Deoxyfrenolicin和Frenolicin B的全合成研究进展

综述了吡喃萘醌类化合物Deoxyfrenolicin和Frenolicin B的全合成方法研究进展,分析了各合成路线的关键,并部分讨论了各种方法的优缺点。参考文献28篇。     

Total synthesis of rac-longamide B

rac-Longamide B has been synthesized in six-steps from known starting materials. The synthesis is highlighted by a novel palladium-catalyzed double allylic alkylation of amidopyrroles with 2-butene-1,4-di-tert-butyl dicarbonate.     

The Total Synthesis of Brevetoxin B: A Twelve-Year Odyssey in Organic Synthesis

The total synthesis of brevetoxin B has been achieved recently after a long search for a suitable pathway. This twelve-year odyssey

1 The Odyssey of Homer, translated by R. Lattimore, Harper Perenial, New York, 1975 . Homer's Odyssey, one of the western world's first two poems (the Iliad is the other), is the tale of the adventures, wanderings, and exploits of Odysseus, a Greek hero of the Trojan war, as he attempts to reach Ithaca, his home island where his wife Penelope awaits him. During his journey Odysseus has an incredible series of adventures and setbacks caused by the anger of the god Poseidon, whose son Odysseus had blinded. Finally, assisted by his patroness, the goddess Athene, Odysseus returns home to Ithaca to find and punish the suitors, evil men who tried to win his wife's hand and who squandered his wealth and corrupted his servants while he was away. Telemachus, Odysseus' son, who had his own share of adventures while growing up, facing the suitors and, looking for his father, joins him in glory and wisdom as they reestablish their throne on Ithaca. Besides Odysseus, other main characters of Odyssey are as follows: Telemachus: The son of Odysseus, who is just entering manhood, is highly conscious of his duties as a prince successor to the throne and protector of his mother as well as the need to live up to his father's reputation as a hero. His actions waver between the immature and the well-thought over as he searches for the truth about his father and desperately appeals to others for help. It is not until towards the end of the story that he exhibits great courage, skills, and confidence and one feels that he is, indeed, the son of Odysseus. Athene: She is the daughter of Zeus, goddess of wisdom, and patroness of arts and crafts. Odysseus is her favorite and protegé and she is his heroine, even though she is a goddess. She plays a leading role in all important events in the narrative, and her spirit and power always influence and assist Odysseus and Telemachus in their difficult moments. A friend and a confidant to Odysseus, she enjoys winning him over and her relationship with him, while the hero adores her and finds special comfort, companionship, and understanding in her. Poseidon: Younger brother to Zeus, god of the sea and of earthquakes, father of Polyphenus the one-eyed Cyclops whom Odysseus blinds. As a ruler of the sea and natural phenomena, Poseidon is able to place many obstacles in front of Odysseus, whom he despises. Poseidon, however, is unable to hold out against the combined pressure of the other gods, particularly Athene, of whom Odysseus is a favorite, and so eventually relents, but not before he repeatedly unleashes his anger. The Cyclops, Scylla, and The Sirens: Some of the superhuman and monstrous characters of the tale who inflicted tremendous tortures and blows at Odysseus and his men, before he finally overcame them. The Suitors: The evil noblemen of Ithaca who attempt to undermine Odysseus, win the hand of his queen, Penelope, and corrupt his palace servants. They succeed partly, wasting away a great deal of Odysseus fortune, but he eventually prevails and punishes them. Ithaca: The island kingdom of Odysseus, most likely located somewhere off the western coast of Greece and the destination of the hero in this adventure. It is interesting to compare places, events, and characters from the Odyssey to those of modern-day total synthesis, an excercise left to the imagination of the reader!

in synthetic organic chemistry was marked by several strategic and tactical routes, and resulted in numerous new synthetic methods. This article is a behind-thescenes account of the total synthesis of brevetoxin B, from its origins at the University of Pennsylvania to its completion at the University of California, San Diego, and The Scripps Research Institute, La Jolla, California.     

First Asymmetric Total Synthesis of Mansonone P and R

An asymmetric total synthesis of Mansonone P and R was achieved. The synthesis highlights an OH substituent at position 2 by Sharpless dihydroxylation of silyl enol ether.     

Concise Total Synthesis of Ivorenolide B

An expeditious route to the potential immunosuppressive lead compound ivorenolide B ( 1 ) is described, which relies on the formation of the distinctive 1,3‐diyne subunit embedded into the 17‐membered framework of this target by ring‐closing alkyne metathesis (RCAM). This key transformation was accomplished with the aid of the molybdenum alkylidyne complex 7 , which turned out to be compatible with the acid sensitive propargylic alcohol substituents as well as the terminal alkyne unit present in the cyclization precursor. As the presence of such functionality had been detrimental for alkyne metathesis until very recently, this example illustrates the excellent application profile of this new catalyst as well as the rapidly increasing scope of the transformation. Its structural outreach can be further increased by subjecting cyclo‐1,3‐diynes to appropriate post‐metathetic transformations, most notably with the help of alkynophilic gold or palladium catalysts. This aspect is illustrated by the conversion of the model compound 4 into various cyclophane products.     

Enantioselective Total Synthesis of Brevetoxin A: Unified Strategy for the B,E, G,and J Subunits

Brevetoxin A is a decacyclic ladder toxin that possesses 5‐, 6‐, 7‐, 8‐, and 9‐membered oxacycles, as well as 22 tetrahedral stereocenters. Herein, we describe a unified approach to the B, E, G, and J rings based upon a ring‐closing metathesis strategy from the corresponding dienes. The enolate technologies developed in our laboratory allowed access to the precursor acyclic dienes for the B, E, and G medium‐ring ethers. The strategies developed for the syntheses of these four monocycles ultimately provided multigram quantities of each of the rings, supporting our efforts toward the completion of a convergent synthesis of brevetoxin A.     

First Stereoselective Total Synthesis of FD‐594 Aglycon

Stereocontrolled access to the hexacyclic core of FD‐594 has been achieved. The key steps include the intramolecular S_NAr reaction for construction of the densely functionalized xanthone skeleton, the stereoselective lactone cleavage using a chiral nucleophile to induce the axial stereochemistry, and the SmI₂‐mediated pinacol cyclization for the stereocontrolled conversion of axially chiral biaryl dialdehyde into the corresponding trans diol.

     

A Total Synthesis of Norhalichondrin B

Four corners : The syntheses of four key building blocks for the total synthesis of norhalichondrin B (see structure) are described. The assembly of these subunits into the natural product is also reported. Key features of the synthesis are the use of the Achmatowicz oxidation/ionic hydrogenation for the synthesis of pyrans and pyranopyrans, and the application of tandem metathesis for the synthesis of pyranopyrans.

     

Asymmetric Total Synthesis of Oxazolomycins B and C

Efforts towards the first total synthesis of (−)-oxazolomycin B and (+)-oxazolomycin C from the intermediate of our previous synthesis of (+)-neoxazolomycin are reported. The syntheses were achieved in a longest linear sequence of 25 steps from the amino acid serine in 3.6 and 2.7 % overall yields, respectively. The efficiency of our approach is derived from silyl triflate-mediated reductive oxazolidine ring-opening and Fürstner's Ru-catalyzed hydrosilylation and protodesilylation reactions. The obtained spectra and optical rotations were in good agreement with those of natural products, thus confirming the structures.     

Total Synthesis of Rubriflordilactone B

Taking advantage of a 6π electrocyclization–aromatization strategy, we accomplished the first and asymmetric total synthesis of rubriflordilactone B, a heptacyclic Schisandraceae bisnortriterpenoid featuring a tetrasubstituted arene moiety. The left‐hand fragment was accessed through a chiral‐pool‐based route, and linked to the right‐hand fragment by a Sonogashira coupling. The cis geometry of the electrocyclization substrates was established by hydrogenation or hydrosilylation of the alkyne. An electrocyclization–aromatization sequence finally built the multisubstituted arene. The hydrosilylation approach was of significant advantage in terms of reaction scale, reproducibility, and intermediate stability. The structure of synthetic rubriflordilactone B was validated by X‐ray crystallographic analysis, and found to be consistent with that reported for the authentic natural product based on an independent X‐ray crystallographic analysis. However, obvious differences in the NMR spectra of the synthetic and authentic samples suggest that the authentic samples subjected to X‐ray crystallography and NMR spectroscopy were two different compounds.