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Reported herein is a stereoselective route to anti -β-hydroxy sulfoxides through the reaction of epoxides with sulfenate anions. Extensive experimental/computational studies revealed the dual special roles of MgBr2 ·OEt2 , serving to generate the bromohydrin alkoxide intermediate, which undergoes nucleophilic attack on the prochiral sulfenate in a diastereoselective manner. The present study has opened a general stereoselective synthetic route to anti -β-hydroxy sulfoxides. [ABSTRACT FROM AUTHOR]

This article discusses the progress made in the enantioselective total synthesis of γ-rubromycin, a Streptomyces antibiotic. The researchers previously reported a successful photoirradiation method using a chiral, non-racemic 1,2-naphthoquinone to produce an enantioenriched spiroacetal. However, in their latest study, they found that the viability of the photochemical reaction depended on the chromophore structure of the quinones. They also observed that the color of the quinones correlated with their reactivity, with yellow or orange quinones being reactive and red or dark red-purple quinones being unreactive. Further studies are being conducted to gain insights into the photoreaction viability and guide substrate design for the synthesis of γ-rubromycin. [Extracted from the article]

Keywords: stereoselective synthesis; pyranonaphthoquinone; naphthazarin; natural product; oxidative lactonization EN stereoselective synthesis pyranonaphthoquinone naphthazarin natural product oxidative lactonization 2011 2016 6 10/09/23 20231024 NES 231024 Graph We have been studying the synthesis of dimeric pyranonaphthoquinones, [1] -naphthocyclinone ( B 1 b ), [5] actinorhodin ( B 2 b ), [10][65] and -actinorhodin ( B 3 b ), [65] antibiotics of historical importance in polyketide biosynthesis (Figure 1). In planning the synthesis of B 9 b , we sought for the robustness of the skeletal assembly, because our previously developed two routes had problems, one of which was the scalability of the substrate synthesis, [1] and the other was the imperfect enantiocontrol. Further elaboration of B 9 b was studied, which not only provided useful information for the dimer synthesis, but also allowed us to complete the syntheses of I ent i -hemi-actinorhodin ( I ent i - B 8 b ) and I ent i -hemi- -actinorhodin ( B 12 b ). Recent studies on the actinorhodin biosynthesis revealed that the monomer unit undergoes hydroxylation at C6, and hemi-actinorhodin ( B 8 b ), thus generated, serves as the substrate for enzyme-mediated dimerization (Scheme 1). [Extracted from the article]

We report the enantioselective total syntheses of preussomerins EG1, EG2, and EG3. The key transformation is a stereospecific photochemical reaction involving 1,6‐hydrogen atom transfer to achieve retentive replacement of a C−H with a C−O bond, enabling otherwise‐difficult control of the spiroacetal stereogenic center. [ABSTRACT FROM AUTHOR]

This Account showcases three diastereotopos-selective reactions exploited in our complex natural syntheses. 1 Introduction 2 Malyngolide: Hydroalumination of Bisalkynyl tert -Alcohols 3 Cavicularin: Acetal Cleavage 4 Carthamin: Bromoacetoxylation 5 Conclusions [ABSTRACT FROM AUTHOR]

We report an improved synthesis of a C -Glycosyl quinochalcone that is a key intermediate in our total synthesis of carthamin, a natural red pigment of traditional heritage. The C -glycosyl quinochalcone is prepared by regioselective de- O -methylation of a C -glycosyl bromodienone, and installation of a p -coumaroyl side chain through an O → C acyl rearrangement. [ABSTRACT FROM AUTHOR]

Toward a total synthesis of acremoxanthone A, we report a model study on the construction of the EFG ring system. The key steps include (1) an intermolecular 1,3-dipolar cycloaddition of an aryl nitrile oxide with a dienone, and (2) an SN Ar reaction for construction of the F ring. [ABSTRACT FROM AUTHOR]

Toward a stereoselective total synthesis of the lactonamycins, we recently reported an approach to the DEF-ring system. Here we report a model study for constructing the ABCD-ring system, revealing a viable approach through (1) construction of the C-ring by asymmetric benzoin cyclization, (2) introduction of an angular hydroxy group through oxidation of an isoxazolium salt, and (3) construction of the AB rings through a ring-opening/closing sequence. [ABSTRACT FROM AUTHOR]