Semisynthesis of Taxol (R): an improved procedure far the isolation of 10-deacetylbaccatin III

From the needles of domestic yew, (Taxus baccata), 10-deacetylbaccatin III (10-DAB) call be isolated in quantities of up to 297 mg per kg of fresh needles. Additional quantities of 10-DAB call be obtained from the extract by NaBH4 mediated reductive hydrolysis of baccatin esters. A four-step procedure converts 10-DAB into taxol in 58% overall yield

Stereoselektivne sinteze α-hidroksi-β-aminokiselina iz prirodnih hiralnih prekursora

A method for the stereoselective homologation of -amino acids into syn-α-hydroxy-β-amino acids is described, based on the conversion of stereoisomeric cyanohydrins into trans-oxazolines. The synthetic potential of the method is illustrated in the enantioselective formal synthesis of Bestatin.Opisana je metoda za stereoselektivnu sintezu α-hidroksi-β-aminokiselina syn-konfiguracije, polazeći od α-aminokiselina, kao prirodnih hiralnih prekursora. Enantioselektivnost procesa zavisi od strukture polazne aminokiseline, kao i reakcionih uslova. Primena ove metode ilustrovana je u sintezi (2S,3R)-3-amino-2-hidroksi-4-fenilbutanske kiseline, konstituenta nekoliko važnih biološki aktivnih jedinjenja

Intramolekulska Barbier-ova reakcija u vodi - sinteza petočlanih i šestočlanih prstenova

Zinc or indium promoted intramolecular Barbier reactions of aldehydes containing a suitably positioned allylic or propargylic halide unit afford unsaturated cyclic alcohols in moderate yields.Aldehidi koji u pogodnom položaju poseduju alil-halogenidnu ili propargil halogenidnu strukturnu jedinicu reaguju u vodenim uslovima sa cinkom ili indijumom, pri čemu nastaju nezasićeni ciklični alkoholi u umerenim prinosima

Synthesis of vinyldihydropyran by cooperative catalysis

Delta(5)-Unsaturated aldehydes with a suitably positioned allylic halide, or phosphate, leaving group undergo doubly-catalyzed cyclization to give dihydropyran derivatives. The cyclization proceeds under the synergetic action of diazabicycloundecene and Pd(PPh3)(4). This type of transformation was also accomplished with an aryl ketone

Synthetic studies towards d-modified paclitaxel analogues

A synthetic sequence has been developed for the preparation of 9,10-O-diacetyl-4-desmethylene-4β-(3-butenyl)-4α-hydroxy-5-O-mesyltaxicin I-1,2-carbonate 3, an intermediate in the attempted synthesis of cyclobutane paclitaxel analogue. A series of reactions of 3 has been investigated, including the protection of sterically hindered C-4α hydroxy group and oxidative cleavage of the terminal double bond. Cyclization of 13 to the cyclobutane-containing intermediate failed due to unexpected instability of the DMS protecting group under basic conditions. [Acknowledgments. Financial support of the Ministry of Education and Science of the Republic of Serbia is acknowledged (Project No. 172027)

Stereoselective synthesis of (-)-cytoxazone and (+)-epi-cytoxazone

Optically pure (-)-cytoxazone was synthesized, starting from methyl p-methoxycinnamate, in six steps and in 31%, overall yield. The required anti-aminoalcohol configuration was established by combining Sharpless asymmetric aminohydroxylation with the configurational inversion of the intermediate amidoalcohol via ail oxazoline. The synthesis of (+)-epi-cytoxazone is also described. (C) 2003 Elsevier Ltd. All rights reserved

Synthesis of vinyldihydropyran by cooperative catalysis

5-Unsaturated aldehydes with a suitably positioned allylic halide, or phosphate, leaving group undergo doubly-catalyzed cyclization to give dihydropyran derivatives. The cyclization proceeds under the synergetic action of diazabicycloundecene and Pd(PPh3)4. This type of transformation was also accomplished with an aryl ketone. [Projekat Ministarstva nauke Republike Srbije, br. ON172027

Total synthesis and biological evaluation of (-)-atrop-abyssomicin C

Enantioselective synthesis of a marine antibiotic (-)-atrop-abyssomicin C was accomplished in 21 steps, in 1.8% overall yield (4%, based on the recovered starting material). The key steps of the synthesis are the formation of the functionalized cyclohexane core by an organocatalyzed Tsuji-Trost reaction, the formation of a tricyclic spirotetronate unit by a gold-catalyzed reaction sequence and the highly efficient eleven-membered ring closure by a Nozaki-Hiyama-Kishi reaction. Biological tests showed all abyssomicin derivatives to possess strong antibacterial activity against methicillin resistant S. aureus strains; however, they also proved to be cytotoxic, both to malignant and to normal somatic cells

Synthesis, biological evaluation, and modeling of a C,D-seco-taxoid

A C,D-seco-paclitaxel derivative 12 was prepared and tested for biological activity. The key step in the synthesis was a free radical fragmentation of the bicyclic tertiary alcohol 7 under the conditions of the hypobromite reaction. The compound 12 showed no activity in the tubulin test. (c) 2005 Elsevier Ltd. All rights reserved

Synthesis of (-)-cytoxazone and (+)-epi-cytoxazone: The chiral pool approach

Immunomodulator (-)-cytoxazone and its epimer (+)-epi-cytoxazone were synthesized starting from (D)-(-)-4-hydroxyphenylglycine. Homologation of the amino acid was achieved via the corresponding aldehyde, by a cyanohydrin reaction. The racemization of highly sensible amido aldehyde was efficiently suppressed when the oxidation of the parent aminoalcohol was performed by a modified Dess-Martin procedure