The total synthesis of spectinabilin and its biomimetic conversion to SNF4435C and SNF4435D

[reaction: see text] A short synthesis of (+/-)-spectinabilin via a trans-selective Suzuki coupling and subsequent Negishi-type methylation, and its biomimetic conversion to (+/-)-SNF4435C and (+/-)-SNF4435D is described.     

Studies on the biomimetic synthesis of SNF4435 C and D

[reaction: see text] The biomimetic synthesis of the bicyclic core of the novel immunosuppresants SNF4435C and SNF4435D is reported. The core framework was efficiently generated from the all-trans tetraene precursor in one step and in good yield.     

A biomimetic synthesis of the skeleton of trigonoliimine C

On basis of biomimetic concepts, the skeleton of trigonoliimine C was readily achieved in five steps from N-phthaloyl tryptamine. This result suggested a useful synthetic strategy for trigonoliimine alkaloids with this unique ring system.     

Total synthesis of lamellarins D, L, and N

Total synthesis of cytotoxic marine alkaloids, lamellarins D, L, and N, has been achieved by using Hinsberg-type pyrrole synthesis and palladium-catalyzed Suzuki-Miyaura coupling of the 3,4-dihydroxypyrrole bistriflate 6 as the key reactions. The total yields of lamellarins D, L, and N from the common intermediate 6 are 54, 58, and 50%, respectively.     

Total synthesis of the epoxyquinol dimer (+)-panepophenanthrin: application of a diastereospecific biomimetic Diels-Alder dimerisation

An asymmetric total synthesis of the novel and structurally complex epoxyquinol natural product (+)-panepophenanthrin has been accomplished, in which a biomimetic Diels-Alder dimerisation is a key step. The key monomeric precursor was assembled by an efficient Stille cross coupling of two readily available building blocks that upon standing underwent a diastereospecific dimerisation cascade in excellent yield.     

The total synthesis of (-)-SNF4435 C and (+)-SNF4435 D

The size and positioning of substituents on a tetraene, along with the Woodward-Hoffmann rules, control the relative stereochemistry at the four adjacent chiral centers that are generated in the 8pi/6pi electrocyclization cascade. A biomimetic synthesis of (-)-SNF4435 C and (+)-SNF4435 D exploits these steric effects and allows confirmation of the predicted absolute stereochemistry of the natural products.     

Novel methodology for the synthesis of the benz[a]anthracene skeleton of the angucyclines using a Suzuki-Miyaura/isomerization/ring closing metathesis strategy

The synthesis of the benz[a]anthracene skeleton of the angucyclines is described. Key steps involve the Suzuki-Miyaura reaction, isomerization of an aromatic allyl substituent to the corresponding styrene, and the use of the ring closing metathesis reaction to construct a benzene ring. For example, exposure of 3-allyl-2-bromo-1,4,5-trimethoxynaphthalene to (2-formyl-4-methoxyphenyl)boronic acid under palladium catalysis conditions resulted in the formation of 2-(3-allyl-1,4,5-trimethoxynaphthalen-2-yl)-5-methoxybenzaldehyde. This 2-naphthyl benzaldehyde then underwent a Wittig reaction to furnish 3-allyl-1,4,5-trimethoxy-2-(4-methoxy-2-vinylphenyl)naphthalene. Isomerization of the allyl group of this compound afforded the diene, (E)-1,4,5-trimethoxy-2-(4-methoxy-2-vinylphenyl)-3-(prop-1-en-1yl)naphthalene. Exposure of the formed diene to the Grubbs II catalyst resulted in the formation of the benzanthracene, 3,7,8,12-tetramethoxytetraphene, which was easily oxidized to the corresponding quinone.     

The first total synthesis and determination of the absolute configuration of chapecoderin A, B and C

The seco- and rearranged-labdanes, chapecoderins A 1, B 2, and C 3 have been synthesized for the first time starting from (S)-(+)-Wieland-Miescher ketone analogue 11. Their absolute configurations have been determined as depicted in the structures 1, 2 and 3.     

A novel and practical synthetic route for the total synthesis of lycopene

A novel route for the total synthesis of lycopene 1 is described. The synthesis is based on: (i) a condensation between 4,4-dimethoxy-3-methylbutanal 4 and methylenebisphosphonic acid tetraethyl ester 5, leading to the C6-phosphonate 6, followed by (ii) a modified Wittig-Horner reaction between 6 and 6-methyl-5-hepten-2-one 7 producing dimethoxy-3,5,9-triene 8, and (iii) another modified Wittig-Horner reaction between C15-phosphonate 2 and C10-triene dialdehyde 3 producing all-E-lycopene. The synthetic steps are easily operated and practical for the large-scale production.     

The journey of total synthesis toward nannocystin Ax

Herein we describe the detail on our full investigations that led to the achievement of the total synthesis of nannocystin Ax, a 21-membered macrocyclic natural product composing of a tripeptide fragment and a polyketide fragment, which featured in 8 longest linear steps in with 13.9% total overall yield. The key synthetic strategy relied on the late-stage stille coupling for the macrolactonization to construct the 21-membered ring, while direct connection between the tripeptide fragment and the polyketide fragment failed. ¹H NMR experiments reveal that nannocystin Ax should exist as conformational mixtures in deuterated solvents.     

The first total synthesis and structural determination of TMC-66

The first total synthesis and structural determination of TMC-66, an ECE inhibitor, was achieved in short steps by efficient construction and coupling of segments. The oxidative coupling with phenols attaching to electron-withdrawing groups was realized with a novel copper(II) reagent.     

Short and stereoselective synthesis of manzacidins A and C, and their enantiomers

A short and stereoselective synthesis of manzacidins A and C, and their enantiomers was achieved via stereoselective hydrogenation reactions of dehydroamino acid esters 5-8 using a chiral Rh catalyst.     

Isolation and total synthesis of two novel metabolites from the fissurellid mollusc Scutus antipodes

There is almost no information on natural products from gastropods in the order Vetigastropoda and nothing at all for the superfamily Fissurellidae (keyhole and slit limpets), which are only partially protected from predation by their shell. Extraction of the Australian fissurellid Scutus antipodes yielded two new compounds, scutinin A [d-sorbityl hexakis(p-hydroxybenzoate)] and scutinin B [2-ethylhexane-1,3-bis(p-hydroxybenzoate)] that were identified by spectroscopic analysis and their structures confirmed by total synthesis. The compounds were found to have antimicrobial activity but no fish antifeedant activity.     

Synthetic studies toward nortriterpenoids of schisandraceae family. Approach to the construction of functionalized C/D and A/B ring units of micrandilactone C and rubrifloradilactone B

Construction of 6/7 fused bicycles featuring C/D rings of micrandilactone C and rubrifloradilactone B is reported through IMDA reaction of properly designed substrates. Also a route to the construction of a tricycle having A/B ring of nortriterpenoids of schisandra family is reported using RCM and a bromonium ion initiated cycloetherification reaction as the key steps.     

The first total synthesis and structural determination of TMC-264

The first total synthesis and structural determination of TMC-264 has been accomplished. Regioselective bromination, regioselective methoxymethylation, and nickel(0)-Lewis acid-mediated cyclization afforded multi-functionalized 1-methyl-dibenzo[b,d]-pyran skeleton.