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Chuan He Jun Xuan Peirong Rao Pei‐Pei Xie Xin Hong Xufeng Lin Hanfeng Ding 《Angewandte Chemie (International ed. in English)》2019,58(15):5100-5104
A concise and divergent approach for the total syntheses of four cembrane diterpenoids, namely (+)‐sarcophytin, (+)‐chatancin, (?)‐3‐oxochatancin, and (?)‐pavidolide B, has been developed, and it also led to the structural revision of (?)‐isosarcophytin. The key steps of the strategy feature a double Mukaiyama Michael addition/elimination, a Helquist annulation, two substrate‐controlled facial‐selective hydrations, and a pinacol rearrangement. The described syntheses not only achieved these natural products in an efficient manner, but also provided insight into the biosynthetic relationship between the two different skeletons. 相似文献
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Gui‐Yang Chen Huang Huang Dr. Jian‐Liang Ye Dr. Ai‐E Wang Hui‐Ying Huang Prof. Dr. Hong‐Kui Zhang Prof. Dr. Pei‐Qiang Huang 《化学:亚洲杂志》2012,7(3):504-518
The first enantioselective synthesis of cytotoxic natural products rigidiusculamides A (ent‐ 21 ) and B ( 8 ) has been achieved by two synthetic routes. The first one is convergent based on the common intermediate 11 , obtained through a high yielding SmI2‐mediated Reformatsky‐type reaction. A highly diastereoselective one‐pot Dess–Martin periodinane‐mediated bis‐oxidation allowed the direct conversion of the diastereomeric mixture of 11 into rigidiusculamide B ( 8 ). Isolation of minor diastereomer 21 , in combination with computational work, allowed us to suggest the structure of the natural rigidiusculamide A to be 21 , as synthesized by the second route. Four diastereomers ( 7 , 7 , 22a , and 22b ) and an enantiomer ( 21 ) of rigidiusculamide A ( 21 ) have been synthesized. On the basis of literature precedents and computational work, a biosynthetic pathway for rigidiusculamides A and B was proposed to account for the opposite configuration at C‐5 of those two congeners. 相似文献
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When epi isn't! The first total synthesis of the reported structures of 9-epi-presilphiperfolan-1-ol and presilphiperfolan-1-ol has been achieved. Key steps are a catalytic asymmetric alkylation of a novel diene-containing electrophile followed by a two-carbon ring contraction and an intramolecular Diels-Alder cycloaddition to form the stereochemically dense tricyclic core. The synthetic work has resulted in the structural revision of presilphiperfolan-1-ol. 相似文献
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Allen Y. Hong Brian M. Stoltz 《Angewandte Chemie (International ed. in English)》2014,53(21):5248-5260
Presilphiperfolanols constitute a family of biosynthetically important sesquiterpenes which can rearrange to diverse sesquiterpenoid skeletons. While the origin of these natural products can be traced to simple linear terpene precursors, the details of the enzymatic cyclization mechanism that forms the stereochemically dense tricyclic skeleton has required extensive biochemical, computational, and synthetic investigation. Parallel efforts to prepare the unique and intriguing structures of these compounds by total synthesis have also inspired novel strategies, thus resulting in four synthetic approaches and two completed syntheses. While the biosynthesis and chemical synthesis studies performed to date have provided much insight into the role and properties of these molecules, emerging questions regarding the biosynthesis of newer members of the family and subtle details of rearrangement mechanisms have yet to be explored. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(17):4787-4791
Ansellane‐type sesterterpenoids including, ansellones A‐G and (+)‐phorbadione are structurally novel marine secondary metabolites which exhibit anticancer and anti‐HIV activity. The first, asymmetric total syntheses of three structurally representative members, (−)‐ansellones A and B and (+)‐phorbadione, were accomplished in 16–23 steps from (+)‐sclareolide. The route features the first regioselective cyclization of vinyl epoxides with internal alcohol nucleophiles in a 1,4‐addition manner (SN2′). Additionally, the allylic C−H oxidation was exploited at a late stage of the synthesis of (−)‐ansellone A and (+)‐phorbadione. This strategy is expected to be applicable to the synthesis of other ansellane sesterterpenoids. 相似文献
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Jie Wang Chuning Guo Yaqian Liu Dr. Yunpeng Ji Dr. Hongli Jia Prof. Dr. Houhua Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(15):e202400478
The 1,3-dienyl-5-alkyl-6-oxy motif is widely found in various types of bioactive natural products. However, present synthesis is mainly non-asymmetric which relied upon different olefination or transition metal-catalyzed cross-coupling reactions using enantioenriched precursors. Herein, based upon a newly developed enantioselective α-alkylation of conjugated polyenoic acids, a variety of 1,3-dienyl-5-alkyl-6-oxy motif (with E-configured internal olefin) was generated as the corresponding α-adducts in a highly enantioselective and diastereoselective manner. Utilizing 1,3-dienyl-5-alkyl-6-oxy motif as key intermediates, we further demonstrated their synthetic potential by expedient total syntheses of three types of natural products (glutarimide antibiotics, α-pyrone polyketides and Lupin alkaloids) within 4–7 steps. 相似文献
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Substrate‐Controlled Asymmetric Total Syntheses of Microcladallenes A,B, and C Based on the Proposed Structures
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Dr. Te‐ik Sohn Prof. Dr. Deukjoon Kim Prof. Dr. Robert S. Paton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15988-15997
Substrate‐controlled asymmetric total syntheses of (+)‐microcladallenes A, B, and C have been accomplished based on the proposed structures. The syntheses of microcladallenes A and B confirmed the structures and absolute configurations of both natural products. However, the synthesis of microcladallene C, which includes seven stereogenic centers and an (R)‐bromoallene in its compact C15 framework, brought the realization that its proposed structure must be revised. The introduction of C12‐bromine into these natural products with retention of configuration relied on TiBr4‐mediated nucleophile‐assisting leaving group brominations, the stereochemical outcome of which could be attributed, at least in part, to an oxonium or halonium ion formation–fragmentation sequence through intricate neighboring group participation. In addition, the pivotal β‐oriented vicinal cis‐dichloride function in microcladallene C was elaborated through a novel tandem Cl2‐induced electrophilic cyclization/imidate chlorination process. The positive rotations of these natural products with an (R)‐bromoallene constitute exceptions to Lowe’s rule for reasons yet to be determined. 相似文献
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Kento Nishikibe Keisuke Nishikawa Momochika Kumagai Matsumi Doe Yoshiki Morimoto 《化学:亚洲杂志》2022,17(1):e202101137
There are marine cytotoxic bromotriterpenoids, named the thyrsiferol family that are structurally characterized by some tetrahydropyran (THP) and tetrahydrofuran (THF) rings. The thyrsiferol family belongs to natural products that are often difficult to determine their stereostructures even by the current, highly advanced spectroscopic methods, especially in acyclic systems including stereogenic tetrasubstituted carbon centers. In such cases, it is effective to predict and synthesize the possible stereostructures. Herein, to elucidate ambiguous stereostructures and unassigned absolute configurations of aplysiol B, laurenmariannol, and saiyacenol A, members of the thyrsiferol family, we carried out their asymmetric chemical syntheses featuring 6-exo and 5-exo oxacyclizations of epoxy alcohol precursors and 6-endo bromoetherification of a bishomoallylic alcohol. In this paper, we report total assignments of their stereostructures through their asymmetric chemical syntheses and also their preliminary cytotoxic activities against some tumor cells. These results could not have been achieved without depending on asymmetric total synthesis. 相似文献
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Phormidolides B and C,Cytotoxic Agents from the Sea: Enantioselective Synthesis of the Macrocyclic Core
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Dr. Adriana Lorente Alejandro Gil Dr. Rogelio Fernández Dr. Carmen Cuevas Prof. Fernando Albericio Prof. Mercedes Álvarez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):150-156
New cytotoxic polyketide macrolides named phormidolides B and C were isolated from a marine sponge of the Petrosiidae family collected off the coast of Pemba (Tanzania). The isolation, structure elucidation, and enantioselective synthesis of three diastereomers of the macrocyclic core is described herein. The described synthetic methodology started from 2‐deoxy‐D ‐ribose or 2‐deoxy‐L ‐ribose and afforded the desired macrocycles with high enantiomeric purity. The key step of the synthesis is the formation of the Z‐trisubstituted double bond using a Julia–Kocienski olefination. The versatility of the synthetic methodology may provide access to other enantiopure macrocycles by making changes in the starting materials or chiral inductors. 相似文献
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Nathan B. Bennett Prof. Brian M. Stoltz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(52):17745-17750
Access to the bicyclo[5.3.0]decane core found in the daucane and sphenolobane terpenoids via a key enone intermediate enables the enantioselective total syntheses of daucene, daucenal, epoxydaucenal B, and 14‐para‐anisoyloxydauc‐4,8‐diene. Central aspects include a catalytic asymmetric alkylation followed by a ring contraction and ring‐closing metathesis to generate the five‐ and seven‐membered rings, respectively. 相似文献
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Hui Shao Xiaonan Gao Zhong‐Tian Wang Ziwei Gao Yu‐Ming Zhao 《Angewandte Chemie (International ed. in English)》2020,59(19):7419-7424
A divergent synthetic approach to six Ganoderma meroterpenoids, namely ganocins A–C, ganocochlearins C and D, and cochlearol T, has been developed for the first time. This synthetic route features a two‐phase strategy which includes early‐stage rapid construction of a common planar tricyclic intermediate followed by highly selective late‐stage transformations into various Ganoderma meroterpenoids. Key to the strategy are a bioinspired intramolecular hetero‐Diels–Alder reaction and Stahl‐type oxidative aromatization, allowing efficient formation of the common tricyclic phenol intermediate. A nucleophilic dearomatization of the phenol unit, combined with a regioselective 1,4‐reduction of the resulting dienone, enabled rapid access to ganocins B and C. Additionally, site‐selective Mukaiyama hydration, followed by an intramolecular oxa‐Michael addition/triflation cascade, served as a key strategic element in the chemical synthesis of ganocin A. 相似文献
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Protecting‐Group‐Free Enantioselective Synthesis of (−)‐Pallavicinin and (+)‐Neopallavicinin
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Bin Huang Lei Guo Prof. Yanxing Jia 《Angewandte Chemie (International ed. in English)》2015,54(46):13599-13603
The first enantioselective synthesis of (?)‐pallavicinin and (+)‐neopallavicinin has been achieved in 15 steps. The described synthesis avoids protecting‐group manipulations by synthesis designs predicated on highly chemo‐ and stereoselective transformations. Highlights of the synthesis include a palladium‐catalyzed enantioselective decarboxylative allylation to form the chiral all‐carbon quaternary stereocenter, a palladium‐catalyzed oxidative cyclization to assemble the [3.2.1]‐bicyclic moiety, and an unprecedented LiBHEt3‐induced fragmentation/protonation of an α‐hydroxy epoxide to form the α‐furan ketone with the desired configuration. 相似文献