A concise and improved synthesis of (+)-eleutherin, (+)-allo-eleutherin and a formal synthesis of (+)-nocardione B

A concise and improved stereoselective synthesis of (+)-eleutherin, (+)-allo-eleutherin and the formal synthesis of (+)-nocardione B is described. The synthesis is based on a Dötz benzannulation and an improved oxa-Pictet-Spengler cyclization as the key steps. The synthesis is achieved in six steps in overall yields of 18% for eleutherin and 20% for allo-eleutherin.     

First total synthesis of rhuscholide A,glabralide B and denudalide

The first total synthesis of rhuscholide A, a benzofuran lactone possessing anti-HIV-1 activity, had been accomplished in 14 linear steps with 10.6% overall yield. In this synthesis, base-mediated phenol ortho-alkylation and piperidine promoted aldol condensation were exploited as key steps. The synthesis was flexible and allowed for the convenient preparation of two analogous natural products glabralide B and denudalide.     

A short enantioselective synthesis of (+)-eleutherin, (+)-allo-eleutherin and a formal synthesis of (+)-nocardione B

A short enantioselective synthesis of (+)-eleutherin, (+)-allo-eleutherin and the formal synthesis of (+)-nocardione B is described. The synthesis is completed in six steps in overall yields of 8% for eleutherin and 14% for allo-eleutherin. The synthetic strategy features an efficient combination of the Dötz annulation reaction with a chiral alkyne and an oxa-Pictet Spengler reaction as the keys steps in the stereodivergent synthesis of (+)-eleutherin and (+)-allo-eleutherin. The synthesis of (S)-(+)-2-(2′-hydroxypropyl)-5-methoxy-1,4-naphthoquinone entails the formal synthesis of (+)-nocardione B.     

An improved synthesis of ‘octa-acid’ deep-cavity cavitand

An improved synthesis of a water-soluble deep-cavity cavitand (octa-acid, 1) is presented. Previously (Gibb, C.L.D.; Gibb, B.C. J. Am. Chem. Soc. 2004, 126, 11408–11409), we documented access to host 1 in eight (non-linear) steps starting from resorcinol; a synthesis that required four steps involving chromatographic purification. Here, we reveal a modified synthesis of host 1. Consisting of seven (non-linear) steps, this new synthesis involves only one chromatographic step, and avoids a minor impurity observed in the original approach. This improved synthesis is therefore useful for the laboratories that are investigating the properties of these types of host.     

Total synthesis of BE-43547A2

An asymmetric total synthesis of BE-43547A₂ has been achieved in 16 steps (longest linear) on a 3.2 gram scale. The details of our efforts that led to the total synthesis of BE-43547A₂ were reported, the final 6 steps were optimized, and the overall yield was improved from 4.5% to 9.7%. The procedure utilized in the final 2 steps may serve as a better method for separating unstable APD compounds.     

An efficient total synthesis of 9-methoxycarbazole-3-carbaldehyde based on a novel methodology for the preparation of methoxyindoles

A direct synthesis of naturally occurring 9-methoxycarbazole-3-carbaldehyde 1, based on our methodology for the synthesis of 1-methoxyindoles, is reported. A novel benzannulation strategy was employed using ring closing metathesis as the key step in this total synthesis. The synthesis of the natural product 1 has been achieved in seven steps in 14% overall yield from commercial materials and in only four steps from a methoxyindole compound obtained using the new methodology.     

Total Synthesis of Gracilioether F: Development and Application of Lewis Acid Promoted Ketene–Alkene [2+2] Cycloadditions and Late‐Stage C?H Oxidation

The first synthesis of gracilioether F, a polyketide natural product with an unusual tricyclic core and five contiguous stereocenters, is described. Key steps of the synthesis include a Lewis acid promoted ketene–alkene [2+2] cycloaddition and a late‐stage carboxylic acid directed C(sp³) H oxidation. The synthesis requires only eight steps from norbornadiene.     

Total Synthesis of Gracilioether F: Development and Application of Lewis Acid Promoted Ketene–Alkene [2+2] Cycloadditions and Late‐Stage CH Oxidation

The first synthesis of gracilioether F, a polyketide natural product with an unusual tricyclic core and five contiguous stereocenters, is described. Key steps of the synthesis include a Lewis acid promoted ketene–alkene [2+2] cycloaddition and a late‐stage carboxylic acid directed C(sp³)? H oxidation. The synthesis requires only eight steps from norbornadiene.     

Stereoselective Solid-Phase Synthesis of β-Lactams—A Novel Cyclization/Cleavage Step towards 1-Oxacephams

Despite the antibiotic activity and the attractiveness of β-lactams, the solid-phase synthesis of this class of compounds has been barely reported. Now the diastereoselective synthesis of the 1-oxacepham 2 from the resin-bound β-lactam derivative 1 has been achieved in five steps. The synthesis of 2 and other 1-oxacephams is attractive because all the reaction steps proceed in high yield, the purity of the product is high, and the reaction sequence is simple.     

The first stereoselective synthesis of dendrodolide A

The first stereoselective total synthesis of natural product, dendrodolide A (1) is described from readily available (R)-propylene oxide and 3-buten-1-ol as starting materials. The synthesis was achieved in 10 steps with an overall yield of 19.1%. The key steps involved in the synthesis are Jacobsen hydrolytic kinetic resolution, epoxide ring opening with 2-allyl-1, 3-dithiane, Yamaguchi esterification, and ring-closing metathesis (RCM).     

Facile synthesis of a pentasaccharide repeating unit corresponding to the common O-antigen of Salmonella enterica O57 and Escherichia coli O51

A concise chemical synthetic strategy has been developed for the synthesis of a pentasaccharide present in the O-antigen of Salmonella enterica O57 and Escherichia coli O51 strains. A sequential glycosylation strategy has been adopted for the synthesis of the target pentasaccharide. All intermediate steps are high yielding and the glycosylation steps are stereoselective. A number of recently developed methodologies have been used in the synthesis.     

Diastereoselective synthesis of (+)-nephrosterinic acid and (+)-protolichesterinic acid

A diastereoselective synthesis of (+)-nephrosterinic acid and (+)-protolichesterinic acid, common members of the paraconic acids is described. The synthesis is based on a diastereoselective orthoester Johnson–Claisen rearrangement of a (Z)-allyl alcohol with a vicinal dioxolane moiety as key steps. The synthesis is completed in 10 steps and with overall yields of 15.9% for (+)-nephrosterinic acid and 16.4% for (+)-protolichesterinic acid.     

Unified route to asymmetrically substituted butenolide, maleic anhydride, and maleimide constituents of Antrodia camphorata

The first synthesis of antrocinnamomin D and a new synthesis of antrodins A and B have been achieved in 6-8 steps and high overall efficiency (51, 46, and 43%, respectively) from commercially available methyl 4-hydroxyphenylacetate. Key steps include Fürstner-Kochi iron-catalyzed sp²-sp³ cross-coupling and 2-silyloxyfuran oxyfunctionalization.     

A short convergent synthesis of the [3.2.1]dioxabicyclooctane subunit of sorangicin A via regioselective epoxide opening

In this paper, we disclose the synthesis of the dioxabicyclo[3.2.1]octane subunit of the potent antibiotic sorangicin A. The synthesis was achieved in a convergent manner in 8 steps. Regio- and stereoselective intermolecular epoxide opening, ring-closing metathesis and iodo-etherification are key steps. cis-2-Butene diol has been employed as a common staring material.     

First total synthesis of salinipyrone A using highly stereoselective vinylogous Mukaiyama aldol reaction

A synthetic approach for the total synthesis of salinipyrone A has been developed. Key steps involve the TiCl₄-mediated vinylogous Mukaiyama aldol reaction (VMAR) of chiral ketene silyl N,O-acetal with propionaldyhyde, an aldol condensation, Witting olefination, and a cyclization. The synthesis proceeds in eight steps.     

A Concise Total Synthesis of the Fungal Isoquinoline Alkaloid TMC-120B

Recent reports of antiepileptic activity of the fungal alkaloid TMC-120B have renewed the interest in this natural product. Previous total syntheses of TMC-120B comprise many steps and have low overall yields (11–17 steps, 1.5–2.9% yield). Thus, to access this compound more efficiently, we herein present a concise and significantly improved total synthesis of the natural product. Our short synthesis relies on two key cyclization steps to assemble the central scaffold: isoquinoline formation via an ethynyl-imino cyclization and an intramolecular Friedel-Crafts reaction to form the furanone.     

Stereoselective synthesis of the C3–C12 subunit of laulimalide

A stereoselective synthesis of the C3–C12 subunit of the tumor growth inhibitors laulimalide is disclosed. The key steps of the synthesis include asymmetric alkylation using Oppolzer’s protocol and an asymmetric hetero-Diels–Alder reaction using Jacobsen’s catalyst. Substrate controlled diastereoselective Luche reduction followed by Ferrier type reactions are other key steps.     

一个改进的Dallacker双内酯的合成

以5步反应从邻碘苯甲酸乙酯合成了9,10-二氢-9,9,10,10-双(γ-丁内酯)菲,减少了3步反应,总产率提高7%.又由邻碘苯甲酰氯与乙烷-1,1,2-三羧酸三乙酯缩合,继以消除两个乙酯基合成Dallacker双内酯,反应减少一步,产率则增高13%.还研究了联苯-2,2-二甲酰氯分别与乙烷-1,1,2-三羧酸三乙酯和氰基琥珀酸二乙酯的缩合,均能得到良好的产率.     

The first stereoselective synthesis of orostanal isolated from a marine sponge Stelletta hiwasaensis

The synthesis of orostanal, containing novel 6-5-6-5 fused rings and exhibiting meaningful bioactivity against HL-60 cells, has been achieved via 12 steps in 18% total yield from a readily accessible intermediate 7. The key steps for the synthesis entailed an alumina-mediated intramolecular aldol cyclization and asymmetric crotylation to construct the chirality of carbon-25.     

Synthetic studies on the phorboxazoles: a short synthesis of an epi-C23 tetrahydropyran core

Studies on the synthesis of the anticancer natural products, the phorboxazoles have led to the synthesis of the C21-C32 penta-substituted tetrahydropyran core which is epimeric to the natural product at C23. The synthesis was achieved in only seven linear steps. The key steps were the use of a Masamune-Abiko anti-aldol reaction, the formation of a dihydropyran precursor molecule by the use of a new ‘Maitland-Japp-like’ cyclisation, and a highly diastereoselective reductive alkylation of the dihydropyran double bond, to generate the corresponding tetrahydropyran ring in an excellent yield.