Synthesis of naturally occurring bioactive butyrolactones: maculalactones A-C and nostoclide I

Starting from citraconic anhydride (13), a simple multistep (9-10 steps) synthesis of naturally occurring butyrolactones maculalactone A (3), maculalactone B (1), maculalactone C (2) and nostoclide I (4) have been described with good overall yields via dibenzylmaleic anhydride (20) and benzylisopropylmaleic anhydride (27). The two anhydrides 20 and 27 were prepared by S_N2′ coupling reactions of appropriate Grignard reagents with dimethyl bromomethylfumarate (14), LiOH-induced hydrolysis of esters to acids, bromination of carbon-carbon double bond, in situ dehydration followed by dehydrobromination and chemoselective allylic substitution of bromoatom in disubstituted anhydrides 19 and 26 with appropriate Grignard reagents. The NaBH₄ reduction of these anhydrides 20 and 27 furnished the desired lactones 21 and 29, respectively. The lactone 21 on Knoevenagel condensation with benzaldehyde, furnished maculalactone B (1), which on isomerization gave maculalactone C (2). Selective catalytic hydrogenation of 1 gave maculalactone A (3). The conversion of lactone 29 to nostoclide I (4) is known.     

Three New Coumarins from Micromelum integerrimum

Micromelum integerrimum (Rutaceae) is a shrub growing in Yunnan Province. Leaves and barks of this plant have been used for the treatment of dysentery, and arthritis1. Previous researches revealed that this plant contained coumarins2-8. Micromelin, the main chemical constituent of this plant, showed significant inhibition against leukaemia P-388 cell line (T/C 149% at 10 mg/kg) but was inactive in lower doses, and also showed significant activity (T/C 228% at 1.25 mg/kg) against Lewis lung…     

Five novel norcembranoids from Sinularia leptoclados and S. parva

Three new norcembrane-based diterpenoids, leptocladolides A (1), B (4) and C (5), along with five known metabolites 6-10, have been isolated from the dichloromethane extract of a Taiwanese soft coral Sinularia leptoclados. Furthermore, a chemical investigation on the dichloromethane extract of S. parva has resulted in the isolation of two new related isomers, 1-epi-leptocladolide A (2) and 7E-leptocladolide A (3), in addition to 1 and 7. The structures of new metabolites 1-5 were elucidated on the basis of extensive spectroscopic analyses and their relative stereochemistries were determined by NOESY experiments. The new metabolites 1 and 3 have been shown to exhibit significant cytotoxic activity against KB and Hepa59T/VGH cancer cell lines.     

Hookerianolides A-C: three novel casbane-type diterpenoid lactones from Mallotus hookerianus

Three highly oxidized casbane-type diterpenoids with unique α,β-unsaturated γ-lactones, named Hookerianolides A (1), B (2), and C (3), were isolated from the methylene chloride extracts of Mallotus Hookerianus. Their structures were elucidated based on NMR spectroscopic data and chemical conversions. The stereochemistry was confirmed by combination of ROESY correlations and CD analyses.     

Cladosporium cladosporioides发酵物中的新的化学成分

在生物活性的导向下,我们对Cladosporium cladosporioides菌种的发酵液的化学成分进行了研究,从乙酸乙酯萃取物中共分离得到了4个枝孢菌素类化合物.应用光谱分析方法(尤其是1D、2D NMR及MS)结合文献数据,确定了它们的结构,其中化合物1-3为新的化合物,命名为Cladosporol A-C,化合物4为已知化合物Cladosporol.活性测试结果表明,化合物1-4对Staphylococcus aureus有较强的抑制作用.文献报道该类化合物还是很强的β-1,3-葡聚糖生物合成抑制剂.     

Three new pterocarpans from the aerial parts of Abrus Precatorius

Abstract

Three new pterocarpans, named abrusprecatins A-C (1–3), along with three known ones, namely medicarpin (4), maackiain (5), and 4-hydroxy-3-methoxy-8,9-methylenedioxypterocarpan (6) were isolated from the aerial parts of Abrus precatorius. The structures of these compounds were established by extensive analysis of mass spectrometric data, 1?D and 2?D NMR spectroscopic data. In addition, the absolute configurations were determined by a combination of single crystal X-ray diffraction analysis and circular dichroism spectroscopy.     

Three new dimeric diterpenes from Rhododendron molle

Birhodomolleins A-C (1-3), three novel diterpenoids dimerized from two grayanane diterpenes through an oxygen bridge, were isolated from the flowers of Rhododendron molle. Their structures were elucidated by interpretation of their 1D and 2D NMR and other spectroscopic data. Birhodomollein A (1) contains a rare chloro-substitution on one of the grayanane moieties. These are the first examples of dimeric diterpenes from the Ericaceae family.     

Diterpenoids from Isodon pharicus

A phytochemical investigation of Isodon pharicus led to the isolation of a novel asymmetric ent-kauranoid dimer, bispseurata F (1), and three new diterpenoids, pharicinins A-C (2-4). Their structures were elucidated by extensive spectroscopic analysis. Compound 1 features a unique linkage pattern of C-17 with C-11′ to connect the two monomers. A possible biogenetic pathway of 1 was also proposed. Compounds 3 and 4 exhibited moderate inhibitory activity against NB4 and SH-SY5Y cell lines.     

Four New Diterpenoids from Isodon leucophylla

IsodonleucoPhyll(Dunn)Hara(Labiatae),distributedinthenorthwestareaofYunnanProvince,isusedasfolkmedicineforitsantibacterialandanti-inflanimatoryactivitybylocalpractitioners'.Fromtheleavesofthisplant,fournewent-kauranetypediterPenoids,baiyecrystalA'C1'3andePi-baiyecrystalC4,wereisolated.Thispaperpresentstheirsimctureelucidation.BaiyecrystalA1C26H34O1owasdeterminedbyHRMS(5O6.2157,calc5o6.2l52).Itsmassspectrumshowedthatthemolecularion(wt5O6)was58amumorethanthatofeffusaninD5',aknownkaureno…     

Three new C_(20)-diterpenoid alkaloids from Delphinium anthriscifolium var.savatieri

Three new C20-diterpenoid alkaloids, designated as anthriscifolmines A-C (1-3), together with two known alkaloids denudatine and delgramine, were isolated from the whole herb of Delphinium anthriscifolium var. savatieri. The structures of these new alkaloids were elucidated on the basis of spectral data.