The special sealing mechanism of caprock for Quaternary biogenetic gas in Sanhu area,Qaidam Basin,China

The Quaternary biogenetic gas reservoirs in the east of Qaidam Basin have many characteristics such as late forming time,shallow burial depth,low diagenetic grade,high porosity and high permeability and so on.It cannot be considered as caprock according to the traditional evaluation criterion.However, the large scale and high efficient biogenetic gas reservoirs of the Qaidam Basin are really formed under these kinds of caprocks,so it does have some specialty in its sealing mechanism.Aiming at the special sealing mechanism,some simulating experiments have been done.The research results show that the sealing ability of biogenetic gas caprock is related with water saturation,the caprock that is saturated with salt water can effectively block seepage and diffusion.Furthermore,the multiple reservoir-caprock groups have accumulated sealing effect,causing the formation of big gas fields.The evaluation method with traditional caprock parameters cannot be adopted in evaluating the study area.

Sesquiterpenes from the soft coral Paralemnalia thyrsoides and their biogenetic correlation

Terpenoids are the important secondary metabolites of soft coral. In the investigation of soft corals collected from South China Sea, we have found many cembranoid diterpenes with bioactivity and two rare unique biscembranoid tetraterpenes, i.e. methyl sartortuoate and methyl isosartortuoate. We have suggested a plausible biogenesis pathway for these two tetraterpenoids in the soft coral Sarcophyton tortuosum.Recently, B. F. Bowden et al. obtained one more tetraterpenoid with the similar structure from the same species Australian soft coral. Besides, they isolated one of the probably

Biogenetic Pathways for Marine Terpenoids

A reasonable theoretical elucidation of biogenetic pathways is given for marine ter-penoids——halogenated terpenoids,cernbranolides and tetracyclic tetraterpenoids in marine organisms ac-cording to biogenesis,and the possibility of studying biogenetic pathways by chemical synthesis and molecu-lar probe method is discussed.

Chemistry and biology of Pestalotiopsis-derived natural products

Species within the fungal genus Pestalotiopsis have become a topic of research in many microbial-chemical and pharmacological laboratories because they contain structurally complex,biologically active metabolites.This article is a follow-up to a previous review(Xu,Ebada,and Proksch,Fungal Divers 44:15–31,2010).It focuses particularly on new findings concerning the chemistry and bioactivity of Pestalotiopsis sp.,covering a period ranging from August 2010 to August 2013.Some 160 metabolites were isolated from Pestalotiopsis species during this period and their structures are reported within a biogenetic context.Bioassays showed antitumor,antifungal,and antimicrobial activities to be the most notable bioactivities of secondary metabolites isolated from this genus.The biogenetic pathways associated with the alkaloids,sesquiterpenes,quinines,xanthones,and lactones covered in this review are highlighted.

Alkaloid constituents from the fruits of Flueggea virosa

Three new indole alkaloids, flueindolines A–C(1–3), along with nine known alkaloids(4–12), were isolated from the fruits of Flueggea virosa(Roxb. ex Willd.) Voigt. Compounds 1 and 2 are two new fused tricyclic indole alkaloids possessing an unusual pyrido[1, 2-a]indole framework, and 3 presents a rare spiro(pyrrolizidinyl-oxindole) backbone. Their structures with absolute configurations were elucidated by means of comprehensive spectroscopic analysis, chemical calculation, as well as X-ray crystallography. Chiral resolution and absolute configuration determination of the known compounds 4, 10, and 11 were reported for the first time. The hypothetical biogenetical pathways of 1–3 were herein also proposed.