Total synthesis of solandelactones A, B, E, and F exploiting a tandem Petasis-Claisen lactonization strategy

Solandelactones A, B, E, and F were synthesized using Nozaki-Hiyama-Kishi coupling of iododiene 13 with aldehydes 14 and 99 obtained by oxidation of alcohols 92 and 94. Key steps in the synthesis of 92 and 94 were (i) a Nagao asymmetric acetate aldol reaction of aldehyde 77 with thionothiazolidine 78 to set in place an alcohol that becomes the (7 S) lactone center of solandelactones, (ii) a Simmons-Smith cyclopropanation of 80 directed by this alcohol, and (iii) Petasis methylenation of cyclic carbonate 90 in tandem with a Claisen rearrangement that generates the octenalactone portion of solandelactones. Synthesis of solandelactones A, B, E, and F confirmed their gross structure and absolute configuration at C7, 8, 10, and 14 but showed that alcohol configuration at C11 must be reversed in pairs, A/B and E/F, from the previous assignment made to these hydroid metabolites. Thus, solandelactones A and B are correctly represented by 2 and 1, respectively, whereas solandelactones E and F are 6 and 5. A biogenesis of solandelactones is proposed for these C 22 oxylipins that parallels a hypothesis put forward previously to explain the origin of C 20 cyclopropane-containing algal products.     

Total synthesis of naturally occurring cephalosporolides E/F

A modular total synthesis of cephalosporolides E/F featuring sequential epoxide–alkyne coupling and subsequent highly regioselective gold catalyzed alkynolcycloisomerization of the resulting alkynetetrol to construct the central spiroketal core has been documented.     

Total synthesis of sphingofungin F

[reaction: see text] A concise, stereocontrolled synthesis of sphingofungin F was achieved. Key features involve diastereoselective oxazoline formation catalyzed by palladium(0), MgBr(2)-promoted gamma-alkoxy allylic stannane addition, and palladium(0)-catalyzed coupling of a vinyl iodide with an organozinc reagent.     

Total synthesis of cannabisin F

A practical eight-step synthesis of lignanamide cannabisin F starting from vanillin is reported for the first time. This synthetic strategy applies the aldol reaction followed by the Wittig reaction to afford the key 8-O-4′-neolignan intermediate diacid. The diacid was condensed with N,O-protected tyramine giving, after deprotection, cannabisin F.     

Total synthesis of amphidinolide E

A convergent and highly stereocontrolled synthesis of amphidinolide E (1) has been accomplished. The synthesis features a highly diastereoselective (>20:1) BF3.Et2O promoted [3+2] annulation reaction between aldehyde 3 and allylsilane 4 to afford substituted tetrahydrofuran 2.     

Total synthesis of norleucosceptroids F and G

First total synthesis of norleucosceptroids F and G has been achieved through key steps of Michael–Aldol cascade, oxa-Michael cyclization–dehydration–deprotection cascade and cross metathesis(CM), this work developed a general and concise method to the synthesis of leucosceptroid and norleucosceptroid.     

Total synthesis of (+)-lepadin F

An enantioselective total synthesis of (+)-lepadin F is described. The synthetic sequence features an intermolecular aza-[3 + 3] annulation, homologation of a vinylogous amide via Eschenmoser's episulfide contraction, and a highly stereoselective hydrogenation essential for achieving the 1,3-anti relative stereochemistry at C2 and C8a.     

Total synthesis of (+)-chloranthalactone F

Sequential biomimetic elaborations, featured by CrO(3)-mediated oxidative lactonization, and DDQ-involved oxidative enol-lactonization, ensured the concise total synthesis of (+)-chloranthalactone F.     

Total synthesis of antibiotic streptothricin F

The first total synthesis of streptothricin F was achieved and its structure was unequivocally confirmed.     

Total synthesis of dispyrin, purpurealidin E, and aplysamine-1

Bromotyrosine alkaloids dispyrin (1), purpurealidin E (2), and aplysamine-1 (3) isolated from marine sponge, were synthesized from commercially available tyramine (4) as a common starting material. The overall yield was 18%, 39%, and 22% for 1 from 4 in 5 steps, 2 in 5 steps, and 3 in 6 steps, respectively.     

Total synthesis of isoroquefortine E and phenylahistin

Isoroquefortine E and phenylahistin were synthesized using the Horner–Wadsworth–Emmons reaction as the key step to build the dehydroamino acid moiety. The syntheses provided the materials for the biological studies of the roquefortine–phenylahistin molecules.     

Total synthesis of argyrins A and E

The total synthesis of argyrins A and E were accomplished using a convergent strategy by condensation of one tripeptide and two dipeptide fragments. The synthesis strategy, which was developed for the protection of peptide fragments and identification of the optimum macrocylization site, can be applied to further synthetic studies involving other members of the argyrin family.     

Total synthesis of a novel tetracyclic alkaloid, cassiarin F from the flowers of Cassia siamea

A novel alkaloid, cassiarin F (1), which showed potent antiplasmodial activity against Plasmodium falciparum in vitro, was isolated from the flowers of Cassia siamea, and its structure was elucidated on the basis of 2D NMR analyses. A total synthesis of 1 was also achieved by employing the Suzuki coupling constructing biaryl unit, nucleophilic aromatic substitution, and Houben-Hoesch type ring construction as key steps.     

A modular total synthesis of aculeatins A, B, E, F and 6-epi-aculeatins E, F

The total synthesis of aculeatins A, B, E and F confirming the assigned absolute configuration of recently isolated aculeatins E and F is documented. A convergent approach has been designed by the addition of both the terminal units (phenol and side chain) at an advanced stage. The central 1,3,5-triol unit with the requisite stereochemistry was prepared from the commercially available α-d-glucoheptonic-γ-lactone. Selective O-debenzylation during the hydrogenolysis of the diyne intermediate and the one pot phenolic oxidation with concomitant spiroketalization highlight the accomplished total syntheses.