Synthesis of the tetrahydroisoquinoline alkaloid (+/-)-renieramycin G and A (+/-)-lemonomycinone analogue from a common intermediate

The total synthesis of tetrahydroisoquinoline alkaloids (+/-)-renieramycin G (4) and a lemonomycinone analogue (7) is described. A general strategy to synthesize both the mono- and bistetrahydroisoquinoline alkaloids from a common advanced intermediate, 17, is presented.     

Total synthesis of unsaturated imine venom alkaloids of Costa Rican ant by way of Schmidt reaction via allyl/pentadienyl cations

Total synthesis of α,β-, and α,β,γ,δ-unsaturated imine ant venom alkaloids is described. The labile two conjugated imine alkaloids were synthesized by late stage intramolecular Schmidt reaction via allyl and pentadienyl cation intermediates.     

Pyrrolizidine alkaloids

This review covers a range of pyrrolizidine alkaloids which have been isolated from various natural sources. The synthesis of necines and necic acids is described along with pharmacological and biological studies of pyrrolizidine alkaloids. The literature from July 2000 to June 2001 is reviewed, and 59 references are cited.     

A common approach to pyrrolizidine and indolizidine alkaloids; formal synthesis of (−)-isoretronecanol, (−)-trachelanthamidine and an approach to the synthesis of (−)-5-epitashiromine and (−)-tashiromine

A common and short stereoselective route is described for the formal synthesis of pyrrolizidine alkaloids, (−)-isoretronecanol and (−)-trachelanthamidine. An approach to the synthesis of indolizidine alkaloids (−)-5-epitashiromine and (−)-tashiromine utilizing ring closing metathesis is also described starting from commercially available and inexpensive l-proline.     

Dimerization of (+)-myrmicarin 215B. A potential biomimetic approach to complex myrmicarin alkaloids

The acid promoted diastereoselective dimerization of myrmicarin 215B is described. The reactivity of these sensitive alkaloids, structural assignment, and a possible mechanism for the observed dimerization is discussed. These finding raise the intriguing possibility of the synthesis of the highly sensitive myrmicarin alkaloids based on a strategy involving the direct dimerization of functional tricyclic myrmicarin derivatives.     

A general approach to 3-n-butyl-5-alkylindolizidines: total synthesis of (-)-indolizidine 195B

Indolizidine type alkaloids have been attractive synthetic targets due to their biological activity. The total synthesis of (-)-indolizidine 195B via a general route, which could potentially be used to prepare other indolizidine alkaloids such as (-)-gephyrotoxin 223AB and (-)-myrmicarin 237A, is described.     

Synthesis of (−)-hygrine, (−)-norhygrine, (−)-pseudohygroline and (−)-hygroline via Nef reaction

Synthesis of tropane alkaloids (−)-hygrine, (−)-norhygrine and sedum alkaloids (−)-pseudohygroline and (−)-hygroline is described from l-proline via Henry and Nef reactions.     

Capillary isotachophoresis of some isoquinoline alkaloids

The isotachophoretic behavior of quaternary benzo/c/phenanthridine, protoberberine and aporphine alkaloids in different electrolyte systems is described. The concentration of the leading ion and the pH value of the leading electrolyte affect the relative effective mobilities of the alkaloids. The system of pH 4.7, containing the leading ion K⁺ (0.005 M) counter ion acetate, and the terminating ion β-alanine (0.02 M), has been selected for the quantitative determination of the studied alkaloids in model mixtures and plant extracts.     

1,2,3,4-tetrahydro-8-hydroxymanzamines, alkaloids from two different haplosclerid sponges

The isolation and characterization of two new sponge alkaloids, 1,2,3,4-tetrahydro-2-N-methyl-8-hydroxymanzamine A (2) and 1,2,3,4-tetrahydro-8-hydroxymanzamine A (3), is described. These compounds were obtained from Papua New Guinea sponges of the genera Petrosia and Cribochalina, which are in different families of the order Haplosclerida. These new manzamines are close in structure to 8-hydroxymanzamine (4) recently reported from Pachypellina, a Haplosclerid sponge belonging to a different family than that of the two preceding sponges. The cytotoxicity of 2 is described and the biogenetic relationship of 2 or 3 to manzamine A (1) and to nine other related polycyclic diamine and one monoamine type alkaloids is described.     

血水草生物碱的HPLC分离

建立了内衬聚亚胺型Ｃ１８ 反相高效液相柱分离血水草生物碱ＨＰＬＣ 新方法。 考察了梯度洗脱分离时,起始缓冲液组成及ｐＨ 值对分离的影响。 当用０ ．０２８ ｍｏｌ／Ｌ Ｋ２ ＨＰＯ４（ｐＨ ８ ．５） 为起始洗脱液, 线性梯度洗脱至１００ ％ 甲醇时, 血水草提取液中主要生物碱以及含量较少的生物碱可得到理想分离。 用峰面积归一化法考察不同地点, 不同季节血水草各生物碱含量的变化规律, 为血水草的采收提供了科学依据。     

An approach to the tricyclic core of madangamines based upon a biogenetic scheme

[reaction: see text] A short synthesis of intermediates possessing the tricyclic core of natural madangamines, bioactive alkaloids found in marine sponges, is described. The key reaction entails the condensation of the sodium salt of diethylacetonedicarboxylate with a dihydropyridinium salt derivative. This new approach is modeled on a biogenetic proposal linking madangamines to ircinals, related alkaloids occurring in sponges of the same order.     

New methods for alkaloid synthesis : Generation of indole-2, 3-diquinomethanes as a route to indole alkaloids

The generation of an indole-2,3-quinodimethane intermediate and its use for the synthesis of indole alkaloids is described.     

Synthesis of the 2-aza-7-oxatricyclo[4.3.2.04,8]undecane nucleus of some gelsemium alkaloids

The preparation of a key tricyclic intermediate for the eventual total synthesis of the alkaloids gelsemicine and gelsedine is described.     

Analysis of Norditerpenoid Alkaloids. Extracted from Aconitum sinomantanum Nakai by Electrospray Ionization Tandem Mass Spectrometry

Introduction AconitumsinomantanumNakai(GaowutouinChi nese)isdistributedinthenorthwesternareaofChina,anditsroots(RAS)areexternallyusedasakindof folkmedicineinChina.Themainactiveconstituentsof RASarenorditerpenoidalkaloids.Themajoralkaloid,lappaconitine,was…     

Enantioselective approach to the hetisine alkaloids. Synthesis of the 3-methyl-1-aza-tricyclo[5.2.1.0(3,8)]decane core via intramolecular dipolar cycloaddition

[structure: see text]. An efficient, enantioselective approach to the hetisine class of the C(20)-diterpenoid alkaloids is described. The strategy involves an intramolecular oxidopyridinium dipolar cycloaddition as the key transformation, in which simultaneous formation of the C5-C6 and C10-C20 bonds in the 3-methyl-1-aza-tricyclo[5.2.1.0(3,8)]decane core of the hetisine alkaloids is effected.     

Heteroatom directed photoannulation: synthesis of indoloquinoline alkaloids: cryptolepine, cryptotackieine, cryptosanguinolentine, and their methyl derivatives

A three-step synthesis of indoloquinoline alkaloids is described. The reaction of 2,3 and 4-substituted haloquinolines with anilines afforded the respective anilinoquinolines, which upon photocyclization gave the indoloquinolines. By regioselective methylation on quinoline nitrogen, furnished the alkaloids cryptotackieine, cryptosanguinolentine, cryptolepine, and the synthetic isomer isoneocryptolepine. Their methyl derivatives were also synthesized in search of new antiplasmodial drugs and DNA intercalating agents.     

Ion-pair chromatography with UV absorbing counterions on reversed-phase layers. Part 1: Chromatography with hydroxynaphthalenesulfonic acids

The results of ion-pair chromatography with UV-absorbing counterions are described. Hydroxynaphthalenesulfonic acids are used as ion pair formers, and alkaloids as test samples. The separations are performed on silanized silica gel from Merck and KC₁₈F plates from Whatman. The influence of the counterion on the R_f-value is demonstrated. Some alkaloids exhibit characteristic fluorescence as ion pairs.     

An intramolecular aza-[3+3] annulation approach to azaphenalene alkaloids. Total synthesis of myrrhine

A detailed account on the stereoselective total syntheses of azaphenalene alkaloids via an intramolecular aza-[3+3] annulation strategy is described here. All five members of the Coccinellidae family of defensive alkaloids were prepared from the same common intermediate, which was derived from a stereoselective aza-[3+3] annulation reaction.     

A Facile Chemoenzymatic Approach: One‐Step Syntheses of Monoterpenoid Indole Alkaloids

Facile chemoenzymatic syntheses of cytotoxic monoterpenoid indole alkaloids with novel skeletons and multiple chiral centers are described. Synthesis of these alkaloids was achieved by a simple one‐step reaction using strictosidine and 12‐aza‐strictosidine as the key intermediates. Strictosidines were prepared by coupling of secologanin with tryptamine and 7‐aza‐tryptamine, respectively, using the immobilized recombinant Rauvolfia strictosidine synthase. A detailed stereochemical analysis is presented herein. The results provide an opportunity for a chemoenzymatic approach that leads to an increased diversification of complex alkaloids with improved structures and activities.     

The Lycopodium alkaloids

Lycopodium alkaloids are quinolizine, or pyridine and alpha-pyridone type alkaloids. Some Lycopodium alkaloids are potent inhibitors of acetylcholinesterase (AChE). Huperzine A (HupA) is reported to increase efficiency for learning and memory in animals, and it shows promise in the treatment of Alzheimer's disease (AD). 201 Lycopodium alkaloids from 54 species of Lycopodium (sensu lato) have been reported so far. This review is intended to to cover the chemical, pharmacological and clinical research on Lycopodium alkaloids reported in the literature from the spring of 1993 to August 2004. Structures of 81 new Lycopodium alkaloids are presented, classified and analyzed. The structural characters and biogenetic relationships of the four major Lycopodium alkaloid groups (lycopodine, lycodine, fawcettimine and miscellaneous) are discussed. Bioactivities of Lycopodium alkaloids, especially HupA, are summarized. In particular, the effect of HupA and other cholinesterase inhibitors (anti-AD drugs) on acetylcholine esterase (AChE) activity in the rat cortex and butylcholine esterase activity are compared. Structure-activity relationships and structure modifications of HupA and its analogs are described. Information on clinical trials with HupA and its derivative ZT-1 is presented. The state of HupA availability and recent advances in in vitro propagation of HupA producing plants are outlined. Finally, hypotheses about Lycopodium alkaloid biosynthetic pathways are discussed.