Total synthesis of stephanotic acid methyl ester

[structure: see text]The methyl ester of the naturally occurring macrocyclic pentapeptide stephanotic acid, containing an unusual beta-substituted alpha-amino acid with a tryptophan C-6 to leucine beta-carbon link, has been synthesized. The key steps include the formation of this amino acid through a thioxo-oxazolidine intermediate and a Horner-Wadsworth-Emmons reaction using a phosphonoglycine, derived by a dirhodium(II)-catalyzed N-H insertion reaction, to give a dehydroamino acid and subsequent rhodium(I)-catalyzed asymmetric hydrogenation to introduce the modified tryptophan residue.     

Total synthesis of zincophorin methyl ester

[reaction: see text]. A convergent total synthesis of the methyl ester of zincophorin, an ionophore antibiotic, has been realized relying on a diastereoselective titanium-mediated aldol coupling between the C1-C12 and C13-C25 subunits. The latter fragment was prepared by using a Carroll-Claisen rearrangement.     

Total synthesis of (+) methyl β-d-vicenisaminide

The total synthesis of methyl β-d-vicenisaminide 1 has been achieved. In this approach, the synthesis of enantiomerically pure methyl (4R,5S)- and (4S,5R)-4-azido-5-hydroxy-2(E)-hexenoates 2 was established by enzymatic resolution of (±)-anti-5-acetoxy -4-azido-2(E)-hexenoate 4. Another stereogenic center was introduced by base-catalyzed intramolecular conjugate addition of a hemiacetal-derived alkoxide nucleophile obtained by the reaction of methyl (4S,5R)-N-4-tert-butoxycarbonyl-N-methylamino-5-hydroxyl-2(E)-hexenoate 8 and benzaldehyde in the presence of a base.     

Total synthesis of zincophorin and its methyl ester

A total synthesis of the naturally occurring ionophore zincophorin has been realized. The route features an intramolecular oxymercuration of a cyclopropanemethanol and a Carroll-Claisen rearrangement for the respective elaboration of the C1-C12 and C13-C25 subunits, which have been assembled by using a highly diastereoselective titanium-mediated aldol condensation.     

Semisynthesis of (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid

This paper describes the use of zamoranic acid in the first semisynthesis of the furolabdane (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid, which also establishes the absolute configuration of the natural product. Direct deconjugation of Δ⁷ in zamoranic acid and Bestmann methodology for the furan ring synthesis are the key steps.     

Total synthesis and absolute configuration determination of (+)-subincanadine F

The first asymmetric synthesis of indole alkaloid (+)-subincanadine F was successfully accomplished with the uncommon 7-endo-trig stereoselective radical cyclization as the key step and its absolute configuration was thus assigned.     

Total synthesis and absolute configuration determination of (+)-bruguierol C

The first total synthesis and absolute configuration of bruguierol C are reported. The key step involved the diastereoselective capture of an in situ generated oxocarbenium ion via an intramolecular Friedel-Crafts alkylation.     

Total synthesis of (+)-pederin. 2. Stereocontrolled synthesis of (+)-benzoylselenopederic acid and total synthesis of (+)-pederin

(+)-Benzoylselenopederic acid (1), a left half of (+)-pederin (3), was synthesized stereoselectively based on the Zn(BH₄)₂ reduction and total synthesis of (+)-pederin (3) was accomplished from 1 and the previously synthesized 2.     

Total synthesis of (+)-lysergic acid

A stereocontrolled total synthesis of (+)-lysergic acid (1) is achieved using three metal-catalyzed methodologies for the construction of three key rings. Highlights of the synthesis include Pd-catalyzed indole synthesis to form the B ring, a RCM reaction to form the D ring, and an intramolecular Heck reaction to form the C ring.     

Total synthesis of (+)-bongkrekic acid

Total synthesis of bongkrekic acid, an important apoptosis inhibitor, has been accomplished. The strategy includes inexpensive starting materials, asymmetric alkylation, anionic allyl coupling and oxidative manipulations. This process would provide a sufficient amount of bongkrekic acid and its analogues.     

Total synthesis and determination of the absolute configuration of (+)-neoisoprelaurefucin

The first total synthesis of the seven-membered ring ether marine natural product (+)-neoisoprelaurefucin (1) has been achieved employing a regioselective internal alkylation of amide 3, a novel sequence for removal of the triethylsilyl group from the resulting triethylsilyloxepene 2, and a bromoetherification of alcohol 16 as key steps. In addition, the absolute stereochemistry of the natural product was assigned.     

Total stereospecific synthesis of cis-chrysanthemic methyl ester : the cyclopropenic way.

By cycloaddition of 2-diazopropane to isobutenylpropiolic methyl ester one obtains two isomeric gem-dimethyl 3H-pyrazoles. Both isomers give by photolysis the same cyclopropene which can be selectively hydrogenated to $\text{cis}$-chrysanthemic methyl ester.     

Total synthesis of (+)-zaragozic acid C

A total synthesis of (+)-zaragozic acid C is described. Key features of the synthesis are the use of a double Sharpless asymmetric dihydroxylation reaction of diene 6 to control stereochemistry at four contiguous stereocenters from C3 to C6; the introduction of the C1-side chain by reaction between the anion derived from the dithiane monosulfoxide 27 and the core aldehyde 12; a high yielding, acid-mediated simultaneous acetonide deprotection-dithiane removal-ketalization procedure leading exclusively to the 2, 8-dioxabicyclo[3.2.1]octane core 34; and a novel triple oxidation procedure allowing installation of the tricarboxylic acid.     

Total synthesis of (+)-spiculoic acid A

The total synthesis of natural (+)-spiculoic acid A, a new cytotoxic marine natural product of polyketide origin, has been accomplished for the first time. The key step of the total synthesis was a stereoselective and high-yielding intramolecular Diels-Alder reaction of a highly functionalized (E,E,E)-2,7,9-dodecanal derivative for the construction of the core tetrahydroindan-2-one skeleton.     

Total synthesis of (+)-prelog-djerassi lactonic acid

Optically active Prelog-Djerassi Lactonic Acid $\text{1}$ was synthesized from D-glucal: the crucial point being the elaboration of the carboxylic group as shown in eq. 1 and 2 which involve the sequential process [i] asymmetric addition of methyl anion onto the hetero-olefin 2, [ii] trapping the carbanion intermediate $\text{3}$ [E=Li to SePh] and [iii] oxidative hydrolysis of $\text{3}$$\text{via}$ sila-pummerer rearrangement into $\text{4}$.     

Total synthesis of (+)-FR-900493 and establishment of its absolute stereochemistry

The first total synthesis of (+)-FR-900493, an antibacterial nucleoside antibiotic possessing a 6′-N-alkyl-5′-O-aminoribosyl-glycyluridine structure, is described, and its relative and absolute stereochemistries were established. Key elements of the approach include the early-stage introduction of the aminoribose moiety and two sequential reductive alkylations of an amino group at the 6′-position. This synthetic strategy could be applicable to the synthesis of related nucleoside antibiotics, such as the more potent antibacterial nucleoside antibiotics, muraymycins.     

Total synthesis, structure revision, and absolute configuration of (+)-yatakemycin

The total synthesis of the reported structure 2 for yatakemycin, an exceptionally potent, naturally occurring antitumor agent disclosed in 2003, and its lack of correlation with the natural product are detailed. On the basis of spectroscopic distinctions between 2 and yatakemycin, the natural product structure was reformulated as 3, now bearing a thiomethyl ester versus thioacetate in the left-hand subunit. Total synthesis of 3 provided a compound nearly identical to but still subtly distinct from the natural product. A second reformulation of the yatakemycin structure as 1, incorporating the alternatively substituted right-hand subunit as well as the initial thiomethyl ester reformulation, was confirmed by total synthesis of both (+)- and ent-(-)-1 in studies that also unambiguously established the absolute configuration of the natural product.