First Synthesis of （＋）-2,14-Deoxyalatol from α-Santonin

A novel and general approach for synthesis of the multi-oxygenated dihydrofuran sesquiterpenes has been developed starting from santonin. The key steps involve: the strategic acid-catalyzed double-bond shifting affording 4, the novel base-promoted epoxide rearrangement of 5 generating two key functionals (the C5-OH and the Δ^7,11 double bond), and the stereoselective cyclization of tetrahydrofuran ring without pre-controlling the stereochemistry of C-7. As an example of this approach, synthesis of ( )-2,14-deoxyalatol was described in detail.     

An approach towards the synthesis of sialyl nucleoside mimetics

An approach towards the synthesis of novel sialyl nucleoside mimetics based on d-fructose is described. The synthesis of these mimetics is achieved in good overall yield in seven steps. The key synthetic step is the coupling reaction of pyrimidine bases (uracil, 5-fluorouracil and cytosine) to the C-1 position of the modified d-tagatofructofuranoside.     

Facile enantiodivergent approach to 5-hydroxy-5,6-dihydro-2(1H)-pyridones. First total synthesis of both enantiomers of pipermethystine

[reaction: see text]. A novel enantiodivergent approach to 5-hydroxy-5,6-dihydro-2(1H)-pyridones using a ring closing metathesis and a lipase-mediated kinetic resolution as key steps is described and applied to the first synthesis of both enantiomers of pipermethystine.     

Novel synthesis of enantiomerically pure natural inositols and their diastereomers

A novel synthesis of all stereoisomers of natural inositols has been developed. The key strategy is the stereoselective reduction of substituted β-hydroxy cyclohexanones, which are prepared from a variety of 6-O-acetyl 5-enopyranosides via Ferrier-II reaction catalyzed by palladium chloride. The utility of this approach is demonstrated by the synthesis of D-myo-inositol 1,4,5-tris(phosphate)(IP₃).     

Total synthesis of 3',5'-C-branched nucleosides

[reaction: see text] A novel total synthesis of 3',5'-C-branched uridine azido acid has been accomplished using stereoselective aldehyde alkynylation, Ireland-Claisen rearrangement, and iodolactonization as the key reactions. Compared to traditional routes that start from carbohydrates, the present methodology is more efficient, flexible for future optimization, and provides access to both enantiomers of the products. Because the key chemistry does not involve the 3'- and 5'-C substituents, our route is a general approach to 3',5'-C alkyl nucleoside analogues.     

A new asymmetric synthesis of the natural enantiomer of the indolizidino[8,7-b]indole alkaloid (+)-harmicine

We report a novel, facile and asymmetric approach for the synthesis of the indole alkaloid (+)-harmicine via a highly diastereoselective N-acyliminium cyclization reaction as a key synthetic step, and verify the relative stereochemistry of the key synthetic intermediate in this approach through X-ray crystallography.     

Efficient synthesis of IPL576,092: a novel anti-asthma agent

An enantioseletive synthesis of the novel anti-asthma agent IRL576,092 (2) is described. The synthetic route developed involves stereoselective 1,2-reduction of the enone carbonyl functionality of 6 and subsequent hydroboration as the key steps. Starting from the commercially available 5-androsten-3beta-ol-17-one 3, this approach affords IPL576,092 (2) in nine steps with overall yields of 25%, employing a limited number of chromatographic steps.     

Total synthesis of polyene natural product dihydroxerulin by mild organocatalyzed dehydrogenation of alcohols

Polyene synthesis: An efficient approach to the total synthesis of polyene natural product dihydroxrulin (1) is described. A novel, mild, direct organocatalytic IBX-mediated dehydrogenation process of simple alcohols to enals has been developed, which serves as a key step in the synthesis (see scheme).     

Diastereoselective synthesis of a core fragment of ritonavir and lopinavir

A novel approach to the synthesis of Boc-core, a key starting material for ritonavir and lopinavir involving an unprecedented diastereoselective nitroaldol reaction on β-amino aldehyde is disclosed.     

A novel approach to synthesis of tricyclic diterpenoid

A novel approach has been found and the first total synthesis of (±)-Salvirecognine was accomplished by using it. In which intramolecular cyclization and Friedel-Crafts alkylation took place simultaneously to afford key intermediates for synthesis of aromatic tricyclic diterpenoids.     

Enantioselective synthesis of epi-(+)-Sch 642305: observation of an interesting diastereoselection during RCM

In an approach towards the enantioselective total synthesis of the novel bioactive natural product Sch 642305, an unusual diastereoselection during the key RCM reaction, resulted in the synthesis of the 11-epi-isomer of Sch 642305.     

A new asymmetric synthesis of the anti-tumor alkaloid (R)-(+)-crispine A

We report a novel, facile, and asymmetric approach for the synthesis of the anti-tumor alkaloid (+)-crispine A via a highly diastereoselective N-acyliminium cyclization reaction as a key synthetic step.     

An acid-catalyzed ring-switch reaction of lactams to lactones: concise synthesis of 2,4-dialkyl-3-hydroxybutanolides

A novel approach for the synthesis of 2,4-dialkyl-3-hydroxybutanolides, having three successive stereogenic centers, by an acid-catalyzed ring-switch reaction of 2-(2-hydroxyalkyl)lactams is described. This transformation was applied to the synthesis of the key intermediates of teromerase inhibitor UCS1025A.     

A novel and stereospecific synthesis of (+)-preussin

A novel and stereospecific approach to (+)-preussin that would permit the synthesis of analogs for structure activity relationship studies, is disclosed. The key step includes the regio- and stereoselective elaboration of a bromohydrin via intramolecular sulfinyl group participation.     

Synthesis of A-B-C-ring Tricyclic Core of iso-Merrilactone A

A desymmetrization approach for the synthesis of the A-B-C tricycle intermediate of iso-merrilactone A was described. The key steps of this synthesis to efficiently access the tetracyclic Illicium sesquiterpenes core included an intramolecular aldol cyclization and an oxidative lactonization reaction. A novel Au catalyzed hydrolytic cyclorearrangement cascade reaction was explored in the initial stage.     

Formal synthesis of（＋）-tashiromine and study toward the total synthesis of（＋）-stemoamide

An effcient formal synthesis of（＋）-tashiromine was achieved by employing an intermolecular asymmetric Mannich-type reaction as the key step.Concurrently,a novel approach toward the total synthesis of（＋）-stemoamide through dyotropic rearrangement of 3,4-cis-b-lactone was also explored.     

Synthesis of (S,S)-isodityrosine by Dötz benzannulation

[reaction: see text] A synthesis of (S,S)-isodityrosine 1, a naturally occurring, key structural subunit of numerous biologically active macromolecules, is described. A formal [3 + 2 + 1] cycloaddition (D?tz benzannulation) approach was utilized to simultaneously construct an aromatic ring and the diaryl ether linkage in one step. This key step was extended to the synthesis of (S,S)-isodityrosine in two separate convergent synthetic routes. This method demonstrates a novel and mild method for the synthesis of diaryl ethers.     

Stereoselective formation of Bis(alpha-hydroxy ketones) via enzymatic carboligation

The enzymatic approach to a novel class of chiral bis(alpha-hydroxy ketones) of type 5 and 8, which enable the synthesis of new multidentate ligands for asymmetric transition metal catalysis, is described. The key step is the second benzoylformate decarboxylase catalyzed C-C-bond formation between an aromatic dialdehyde and acetaldehyde, which proceeds with complete stereocontrol. Transformation of enantiomerically enriched monoadduct (S)-4 (ee 88%) and (S)-7 (ee 79%) resulted in optical pure (S,S)-5 and (S,S)-8 besides minor amounts of the corresponding diastereomeric meso-forms.     

Transketolase and fructose-1,6-bis-phosphate aldolase, complementary tools for access to new ulosonic acid analogues

A new approach to the synthesis of ulosonic acids KDO and DAH is described. The key step is the C₅-C₆ bond formation catalysed by fructose-1,6-bisphosphate aldolase (for KDO) or transketolase (for DAH) using substituted acrylonitrile α-hydroxyaldehyde. All asymmetric carbon configurations are determined in an enzymatic step by the means of deshydrogenase or lipase. This strategy, using a non-metabolism pathway, allows access to novel precursors of KDO, DAH and analogues.     

A novel and versatile entry to asymmetrically substituted pyrazines

A novel and convenient procedure for the synthesis of asymmetrically tri- and tetrasubstituted pyrazines starting from para-methoxybenzyl-protected 3,5-dichloro-2(1H)-pyrazinones was elaborated. The key step is the conversion of the intermediate para-methoxybenzyl-protected thiopyrazinone upon treatment with MeI/I(2), into a pyrazine, rendering the chlorine in the C5-position susceptible to substitution. This approach entails the orthogonal introduction of the four substituents of the pyrazine scaffold. The application of microwave irradiation during different steps of the sequence has been shown to be highly valuable for speeding up reactions.