First total synthesis of 1-O-beta-D-glucopyranosyl-5-deoxyadenophorine and its aglycon congener: determination of the absolute configuration

The first total synthesis of the potent glycosidase inhibitors 1-O-beta-D-glucopyranosyl-5-deoxyadenophorine and its aglycon congener is described in respectively 13 steps (9% overall yield) and 9 steps (29% overall yield) from (R)-Garner aldehyde. The synthesis takes advantage of several key reactions including a diastereoselective allylation of a chiral imine, a stereoselective epoxidation, and a glycoside coupling. In addition this study established unambiguously the absolute configuration of the natural products.     

An efficient total synthesis of chrysophanol and the sennoside C aglycon

A rapid synthetic approach to the naturally occurring chrysophanol and the sennoside C aglycon is reported. The method involves a three-step protocol starting with commercially available aloin-A to give the two title compounds.     

Synthetic studies on indolocarbazoles: total synthesis of staurosporine aglycon

A synthesis of staurosporine aglycon and its analogs was achieved in a 28-36% overall yield starting from 2-methylindole. The prominent key steps for the synthesis of the indolocarbazole alkaloids involved electrocyclization and nitrene insertion reactions.     

Total synthesis of the ristocetin aglycon

The first total synthesis of the ristocetin aglycon is described employing a modular and highly convergent strategy. An effective 12-step (12% overall) synthesis of the ABCD ring system 3 from its amino acid subunits sequentially features an intramolecular aromatic nucleophilic substitution reaction for formation of the diaryl ether and closure of the 16-membered CD ring system (65%), a respectively diastereoselective (3:1, 86%) Suzuki coupling for installation of the AB biaryl linkage on which the atropisomer stereochemistry can be further thermally adjusted, and an effective macrolactamization (51%) for closure of the 12-membered AB ring system. A similarly effective 13-step (14% overall) synthesis of the 14-membered EFG ring system 4 was implemented employing a room-temperature intermolecular S(N)Ar reaction of an o-fluoronitroaromatic for formation of the FG diaryl ether (69%) and a key macrolactamization (92%) with formation of the amide linking residues 1 and 2. The two key fragments 3 and 4 were coupled, and the remaining 16-membered DE ring system was closed via diaryl ether formation to provide the ristocetin tetracyclic ring system (15 steps, 8% overall) enlisting an unusually facile (25 degrees C, 8 h, DMF, >/=95%) and diastereoselective (>/=15:1) aromatic nucleophilic substitution reaction that benefits from substrate preorganization.     

First total synthesis of ocimarin

<正>A facile approach for the first synthesis of ocimarin,naturally occurring coumarins,was developed by employing a cerium(Ⅲ) chloride heptahydrate-catalyzed Pechmann condensation of phenols andβ-keto esters in a solvent-free system as key step,by which ocimarin was achieved by three steps starting from acetylacetic ether and resorcinol with total yield 23.2%.All structures of new compounds were confirmed by IR,~1H NMR and MS.     

First total synthesis of heterocurvistone

The sesquiterpene ketone (±)-heterocurvistone was synthesized in eight steps and 12% overall yield from known methyl R-(+)-3-(4-methyl-3-cyclohexen-1-yl)-3-butenoate, readily available from R-(+)-limonene. The key synthetic step is an oxymercuration-induced cyclization.     

First total synthesis of fumaridine

The first total synthesis of the alkaloid fumaridine 1a is reported. The key step is the assemblage of the arylmethylene isoindolinone 2a (E) by Horner reaction between the phosphorylated isoindolinone 3a and the suitably substituted benzaldehyde 4. N-Lactam deprotection and concomitant E→Z isomerization complete the synthesis of the title compound.     

First total synthesis of murisolin

The first and concise total synthesis of murisolin (1) was accomplished using asymmetric alkynylation and Sonogashira coupling as the key steps. The threo/trans/threo-type THF ring moiety was constructed with excellent stereoselectivity by asymmetric alkynylation of 1,6-heptadiyne to alpha-tetrahydrofuranic aldehyde, which was also prepared via the asymmetric alkynylation.     

First total synthesis of tripdiolide

The first total synthesis of tripdiolide 1 from the readily available abietic acid 3 in 22 steps is described and this synthesis furnishes a 5.8% overall yield of 1 with an average yield of 87%.     

First total synthesis of papilistatin

Papilistatin has been isolated recently and found to have good anticancer and antibacterial activity. Papilistatin is a unique phenanthrene-1,10-dicarboxylic acid. The first total synthesis of papilistatin is described here with radical cyclisation as the key step.     

First total synthesis of achaetolide

The first total synthesis of achaetolide, a 10-membered macrolactone was achieved using Mitsunobu reaction and Grubbs ring-closing metathesis reaction as the key steps for ring construction. The desired stereo centres were generated by Jacobsen hydrolytic kinetic resolution, dihydroxylation and Sharpless asymmetric epoxidation reactions.     

First total synthesis of mytiloxanthin

The first total synthesis of mytiloxanthin 2 was accomplished via the cyclopentyl ketone 7 prepared by stereoselective rearrangement of the epoxide 4a.     

First total synthesis of Brevipolide N and total synthesis of Brevipolide M

The First total Synthesis of Brevipolide N and total Synthesis Brevipolide M have been accomplished from commercially available d-Mannitol. The key features of the syntheses are the use of Horner–Wadsworth–Emmons olefination, Noyori reduction, Acid catalyzed epoxide opening and Lindlars reaction.     

A formal synthesis of the auriside aglycon

A highly convergent formal synthesis of the auriside aglycon was achieved. An indene-based thiazolidinethione chiral auxiliary was used for the construction of both the C1-C9 and C10-C17 fragments via acetate aldol reactions. A Meinwald reaction was utilized to install the stereocenter at C2, and a conjugated addition to an ynone was used to construct the C9-C11 enone.     

Total synthesis of the cyanolide A aglycon

The synthesis of the potent molluscicide cyanolide A has been achieved in 10 steps without the use of protecting groups. The synthesis features a key Sakurai macrocyclization/dimerization reaction that simultaneously forms both tetrahydropyran rings and the macrocycle of the natural product.     

(+)-Phorboxazole A synthetic studies. A highly convergent, second generation total synthesis of (+)-phorboxazole A

[structure: see text] A second generation total synthesis of the potent antitumor agent (+)-phorboxazole A (1) has been achieved. The cornerstone of this approach comprises a more convergent strategy, involving late-stage Stille union of a fully elaborated C(1-28) macrocycle with a C(29-46) side chain. The second generation synthesis entails the longest linear sequence of 24 steps, with an overall yield of 4.2%.     

First total synthesis of piperodione and analogs

Piperodione (3), a secondary metabolite previously isolated from the Javanese pepper plant Piper retrofractum in 0.0002% isolated yield was synthesized in a convergent strategy utilizing a Mannich and a Stetter reaction. An over-all yield of 76% could be achieved. Several analogs were prepared by this synthetic sequence. None of the compounds showed a significant cytotoxicity for human tumor cells (photometric sulforhodamine B assay).