BIOMARKERS INDICATING SEDIMENTARY PALEOENVIRONMENTS

Samples involved in this paper are 35 pieces of crude oils and 43 pieces of source rocks, from which a series of biomarkers, capable of indicating paleoecology and paleoenvironment. This will provide a scientific basis for tracing back to sedimenta-y paleoenvironment and paleoecology.     

GEOCHEMISTY OF BICYCLIC ALKANES IN SEDIMENTS, COAL AND CRUDE OILS

By using GC-MS to analyze the extracts of source rocks, coal and crude oil samplesformed in different sedimentary environments in China, New Zealand and Australia, twenty-two compounds of five types of bicyclic alkanes have been dis covered in the samples. Thispaper makes an exposition of stereochemical structure, abundance and distributive features ofthese compounds and their relation to sedimentary environments and thermal evolution. Furt-thermore, it demonstrates how the abundance ratios of bicyclic alkanes to steranes and ter-panes, drimane to homodramane and the relative abundance of C_(15),C_(16),C_(12)-C_(14) series of bicyclic-alkane compounds can be used to judge and determine types of oil and gas forming environ-ments (the depositive environments of source rocks from which the oil and gas wereformed), characteristics of source rocks and degree of maturation.     

Synthesis of sesquiterpenoids of the drimane group from labdane diterpenoids

Data on the partial synthesis of enantiomerically pure sesquiterpenoids of the drimane group, including valuable biologically active natural compounds, from accessible labdane diterpenoids are surveyed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 896–913, May 1997.     

Photodegradation of some 14,15-bisnorlabdene-13-ones, derived from larixol. Synthesis of drimanic dienes with functional groups at C-6

Valuable chiral drimanic dienic synthons have been prepared by a photolytic Norrish type II degradation of the corresponding 14,15-bisnorlabdene-13-ones. Minor by-products with unexpected bi- and tricyclic structures were formed and some of them were isolated and identified.     

Synthesis of 5,6-dehydro-7-oxoisodrimenin from drim-8-en-7-one

The natural drimane sesquiterpenoid lactone 5,6-dehydro-7-oxoisodrimenin was synthesized from drim-8-en-7-one as well as from 7-oxoisodrimenin.     

Two drimane lactones,valdiviolide and 11‐epivaldiviolide,in the form of a 1:1 cocrystal obtained from Drimys winteri extracts

A cocrystal, C₁₅H₂₂O₃·C₁₅H₂₂O₃, (I), obtained from Drimys winteri, is composed of two isomeric drimane sesquiterpene lactones, namely valdiviolide, (Ia), and 11‐epivaldiviolide, (Ib), neither of which has been reported in the crystal form. Both diastereoisomers present three chiral centres at sites 5, 10 and 11, with an SSR sequence in (Ia) and an SSS sequence in (Ib). O—H...O hydrogen bonds bind molecules into chains running along [20] and the chains are in turn linked by π–π stacking interactions to define planar weakly interacting arrays parallel to (001).     

Synthesis of drim-8(9)-en-7-one,drima-5,8(9)-dien-7-one,and their 11,12-dibromo derivatives from norambreinolide

A method was elaborated for the synthesis of polyfunctional compoonds of the drimane series,viz., drim-8(9)-en-7-one, drima-5,8(9)-dien-7-one, and their 11,12-dibromo derivatives, potential intermediates for the synthesis of natural biologically active drimane sesquiterpenoids starting from norambreinolide. The key intermediate of the above drimane compounds is methyl 7-oco-11-homodrim-8(9)-en-12-oate, prepared by electrochemical oxidation of a mixture of isomeric methyl bicyclohomofarnesenoates obtained from norambreinolide.Institutul de Chimie, Academia de Stiinte Republica Moldova, 3 str. Academiei, 277028 Chisinäu, Republica MoldovaTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 216–222, January, 1996.     

New Access to Sesquiterpene Hydroquinones: Synthesis of (+)‐ent‐Chromazonarol

A facile access to optically active (+)‐ent‐chromazonarol ent‐1, isolated from the sponge Disidea pallescens, is reported from commercially available (+)‐manool 4.