Total synthesis of 8-deshydroxyajudazol B

The total synthesis of a stereoisomer of 8-deshydroxyajudazol B (4), the putative biosynthetic intermediate of the ajudazols A (1) and B (2), is described. The key steps in the synthesis included an intramolecular Diels-Alder (IMDA) reaction to secure the isochromanone fragment, a novel selective acylation/O,N-shift to give a hydroxyamide which was cyclized to the oxazole and a high yielding Sonogashira coupling to form the C18-C19 bond. Partial alkyne reduction then afforded the target 4.     

Syntisis of 4-Demethoxy-7, 11-dideoxydaunomycinone

Our continued interest in the total synthesis of natural and unnatural antitumor anthracyclines¹ especially the aglycones such as daunomycinone (1)² and 4-demethoxydaunomycinone (2)³, 11-deoxydaunomycinone (3)⁴ and 4-demethoxy-11-deoxydaunomycinone (4)⁵ led us to probe methods of obtaining these products of absolute enantitomeric purity. Earlier it was demonstrated that the AB ring synthon 5 having a chiral centre on fusion with phthalic anhydride gave 4-demethoxy-7-deoxy-daunomycinone (6) with no loss of optical purity⁶ and the same was further transformed to 2 [7-(S)-9(S)].     

Total synthesis of 8-oxypseudopalmatine and 8-oxypseudoberberine via ring-closing metathesis

Concise synthesis of 8-oxypseudopalmatine and 8-oxypseudoberberine has been achieved using ruthenium-catalyzed ring-closing metathesis (RCM) as the key step, in which the RCM substrates, 3-arylisoquinolinones, were prepared by lithiated cycloaddition reaction with o-toluamides and benzonitriles.     

Total synthesis of both methyl 4a-carba-D-arabinofuranosides

[reaction: see text] The total synthesis of methyl 4a-carba-alpha-D-arabinofuranoside (1) and methyl 4a-carba-beta-D-arabinofuranoside (2) has been achieved starting from D-mannose (5). Key transformations included a ring-closing metathesis of diene 11 employing Schrock's catalyst followed by a stereoselective hydrogenation with Wilkinson's catalyst.     

Total synthesis of some new 4-demethoxyanthracyclinones

Optically active 4-demethoxyanthracyclinoiies (39a-g) bearing a variety of substituents at the 9position have been synthesised by an analogous route to that previously employed by us for (+)-4-demethoxydaunomycinone (5). These novel anthracyclinones have been prepared in sufficient quantity for subsequent glycosidation and biological evaluation.     

Total synthesis of (+/-)-8alpha-hydroxystreptazolone

[reaction: see text] The intramolecular Pauson-Khand reaction of 2-oxazolone derivatives with a suitable pentynyl appendage exclusively gave the corresponding 4-hydroxy-6-substituted-9-oxa-1-azatricyclo[6.2.1.0(5,11)]undec-5-en-7,10-diones. Based on this newly developed Pauson-Khand reaction of 2-oxazolone-alkyne derivatives, the first total synthesis of (+/-)-8alpha-hydroxystreptazolone was accomplished in a highly stereoselective manner.     

Total synthesis of 8-methoxygoniodiol related compounds via chiron approach

The stereoselective synthesis of 8-methoxygoniodiol related compounds was accomplished by using readily available δ-gluconolactone as a chiral source. The stereoselective addition of an aryl Grignard reagent on an aldehyde, stereoselective reduction of a keto group and regioselective opening of a chiral epoxide by ethyl propiolate are the key steps involved in this synthesis.     

Total synthesis and antimalarial activity of symplostatin 4

The first total synthesis of symplostatin 4, a marine cyanobacterium-derived natural product, is described. Notable features of the route include the efficient preparation of three key fragments and final assembly to the natural product via sequential imide and amide couplings. Symplostatin 4 was also demonstrated to possess significant antimalarial activity (ED(50) of 74 nM against Plasmodium falciparum, strain 3D7).     

Total synthesis of gibberellin A4

A general approach to the preparation of 13-deoxy C₁₉ gibberellins has been established with the total synthesis of (±) gibberellin A₄ ($\text{3}$).     

Bis heteroannulation. 8. Total synthesis of (±)-paniculide-A

An efficient synthesis of the title compound 1 has been achieved beginning with 3-methylglutaric anhydride.     

Total synthesis of 2,6-dimethylergolin-8α-amines

A stereoselective total synthesis of the racemic form of the 2,6-dimethylergolin-8ã-amine derivative III , previously obtained semi-synthetically from lysergic acid, is described. Starting from the commercially available tricyclic lactam 1 , the 9,10-didehydroergoline skeleton containing an angular Me group in position 3 (see 18 ) is built up in several steps applying a Woodward D-ring annelation sequence. The introduction of the 8-amino group is achieved with complete diastereoselectivity to give exclusively the 8ã-derivative 22. Subsequently, a Wagner-Meerwein-type migration of the angular Me group yields the 2-methylated 9,10-didehydroergoline derivative 31. The feasibility of this key transformation was tested on the two model systems 4 and 7 prior to the evaluation of the total synthesis. A stereoselective Birch reduction to the trans-fused ergoline, and deacetylation/acylation conclude the total synthesis of the racemic target compound 34. In addition, the resolution of an early intermediate (see 3 ) by chromatography on a chiral stationary phase is presented which demonstrates that the described total synthesis could also be used for the preparation of the biologically active (5R,8S,10R)-enantiomer III .     

Total synthesis of leukotriene (+)-LTB4 from D-mannitol1

A total convergent synthesis of leukotriene (+)-LTB₄ has been carried out via two enantiomerically pure α-hydroxyaldehydes,chiral key intermediates both obtained from D-mannitol and connected at a four carbon atoms interval by Wittig reactions.     

Total synthesis of lycoperdic acid and its C4-epimer

Efficient stereodivergent syntheses of (+)-lycoperdic acid (LPA) and 4-epi-LPA have been achieved based on asymmetric hydrogenation (H₂, Rh/(R,S)-MeBoPhoz) of racemic enamide as a key step.     

Total synthesis of 20-hydroxy- and 20-carboxy-leukotrienes B4

The total synthesis of 20-hydroxy- and 20-carboxy-leukotrienes B₄ (1 and 2) from key intermediates 13, 14 and 15 is described.     

Total synthesis of (3R, 4S)-4-hydroxylasiodiplodin

Abstract

An alternative and concise total synthesis of (3?R, 4S)-4-Hydroxylasiodiplodin has been reported from inexpensive and commercially available 6-heptenal and Orsellinic acid starting materials. The key steps involved in the synthesis are Wittig reaction, Sharpless epoxidation, Yamaguchi esterification and ring-closing metathesis (RCM).     

Total synthesis of 4-F3t-neuroprostane and its 4-epimer

The first synthesis of 4-F_3t-Neuroprostane 1a and its 4-epimer is described. This molecule presents an important contribution to the study of neuronal oxidative stress in DHA-ω3 depleted brain. The key step involves the introduction of two unsaturated side chains into the chiral polyfunctional cyclopentane 4 via E selective HWE reaction and Z selective Wittig olefination for α and ω chains, respectively.     

Total synthesis of 5, 6, 7, 8-tetrahydroquinolines and quinolines

The condensation of 2-ethoxy-2,3-tetramethylene-3,4-dihydro-l,2-pyran with acetal and ethyl orthoformate was studied. The condensation products react with ammonia on -aluminum oxide to form the corresponding tetrahydroquinolines; a mixture of tetrahydroquinolines and quinolines is formed from these condensation products on platinized --aluminum oxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1533–1534, November, 1971     

Total synthesis of 8-desoxy-isocaespitol,A new polyhalogenated sesquiterpene from Laurencia caespitosa

The structure of a new polyhalogenated bisabolene-type sesquiterpene, $\text{2}$, isolated from $\text{Laurencia caespitosa}$ has been elucidated by chemical and spectral means and confirmed by a three-step synthesis starting from commercial farnesol.