scholarly journals Development of a Divergent Route to Erythrina Alkaloids

Synlett ◽  
2020 ◽  
Vol 31 (04) ◽  
pp. 327-333 ◽  
Author(s):  
Jesper L. Kristensen ◽  
Sebastian Clementson ◽  
Mikkel Jessing ◽  
Paulo J. Vital
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
19Th Century ◽  
First Generation ◽  
Second Generation ◽  
Enantioselective Synthesis ◽  
Third Generation ◽  
Synthetic Strategy ◽  
Erythrina Alkaloids ◽  
The 19Th Century

Erythrina alkaloids were identified at the end of the 19th century and today, more than 100 members of the erythrinane family have been isolated. They are characterized by a unique tetracyclic, α-tertiary spiroamine scaffold. Herein we detail our efforts towards the development of a divergent enantioselective synthesis of (+)-dihydro-β-erythroidine (DHβE) – one of the most prominent members of this intriguing family of natural products.1 Introduction2 Synthetic Strategy2.1 First Generation2.2 Second Generation2.3 Third Generation2.3.1 Radical Endgame2.3.2 Completion of the Total Synthesis3 Conclusion

Evolution of a Chemical Strategy Toward the Synthesis of Unsymmetrically Oxidized Nuphar Alkaloids

Synlett ◽  
2019 ◽  
Vol 30 (14) ◽  
pp. 1632-1642
Author(s):  
Jacob J. Lacharity ◽  
Armen Zakarian
Keyword(s):  
Total Synthesis ◽  
First Generation ◽  
Second Generation ◽  
Third Generation ◽  
Successful Strategy ◽  
Synthesis Design ◽  
Sulfonium Ylide ◽  
Chemical Strategy

Here we describe the frustrations, joys, and unexpected turns experienced in our journey toward a successful strategy directed at the total synthesis of unsymmetrically oxidized Nuphar thioalkaloids. While many adjustments were made to our initial synthesis plan, our general approach to the construction of the central bis(spirothiolane) moiety remained unchanged. Specifically, each iteration of our synthesis design involved the formation of the thiaspirane motif through the stereodivergent coupling of a thietane with a metal carbenoid, followed by a Stevens-type rearrangement of the resulting sulfonium ylide.1 Introduction2 First-Generation Strategy3 Second-Generation Strategy4 Third-Generation Strategy5 Conclusion

Pursuit of Enantioselective Synthesis of Heterocycle-Bearing ­Stereocenters: The Development of a Stereocontrolled BINOL-­Catalyzed Conjugate Addition of Organoboron Nucleophiles

Synlett ◽  
2017 ◽  
Vol 28 (16) ◽  
pp. 2093-2109 ◽  
Author(s):  
Jeremy May ◽  
Thien Nguyen ◽  
Truong Nguyen ◽  
Phong Le ◽  
Po-An Chen ◽  
...  
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Functional Groups ◽  
Conjugate Addition ◽  
Enantioselective Synthesis ◽  
Mechanistic Studies ◽  
Synthetic Strategy ◽  
Iterative Development

This account chronicles the iterative development of an enantioselective conjugate addition of organoboron nucleophiles to α,β-unsaturated enones and enals catalyzed by BINOL derivatives. Beginning with a specific application of this transformation to the total synthesis of the flinderole alkaloids, the transformation progressed to encompass a much larger scope of heterocycle-substituted electrophiles. The next phase saw progress toward the use of a broader scope of functional nucleophiles, with application in a strategy to synthesize discoipyrrole D. At each stage of this chronologically organized discussion, key problems, hypotheses, and solutions are presented to show the sources of discovery and solutions to problems as the catalyst and other reaction components were made more reactive. The interplay of target-directed reaction development, efforts to increase the scope of compatible functional groups, mechanistic studies, and empirical exploration is described to illustrate sources of chemical discovery.1 Introduction2 Synthesis of the Flinderole Natural Products3 Indole-Bearing Stereocenters4 Heteroaryl-Bearing Stereocenters5 Bis-Heteroaryl Stereocenters6 Synthetic Strategy for Discoipyrrole D7 Bis-Aryl Stereocenters8 Remaining Challenges9 Conclusion

The Brown Mite, Bryobia arborea Morgan and Anderson (Acarina: Tetranychidae), on Apple in Nova Scotia.: I. Influence of Intratree Distribution on the Selection of Sampling Units. II. Differences in Habits and Seasonal Trends in Orchards With Bivoltine and Trivoltine Populations. III. Distribution of Diapause Eggs. IV. Hatching of Diapause Eggs

1965 ◽  
Vol 97 (12) ◽  
pp. 1303-1318 ◽  
Author(s):  
H. J. Herbert
Keyword(s):  
Nova Scotia ◽  
First Generation ◽  
Second Generation ◽  
Central Area ◽  
Third Generation ◽  
Apple Trees ◽  
Seasonal Trends ◽  
Sample Unit ◽  
The Third ◽  
Selection Of

AbstractIn Nova Scotia one leaf cluster with an adjoining 1 inch of twig taken from the inside of each of 10 apple trees replicated four times is an adequate sample unit to measure the density of the brown mite.The brown mite has one generation with a partial second in some orchards and one with a partial second and partial third in others. The first generation adults in the bivoltine and trivoltine populations lay summer eggs on the leaves and twigs, and diapause eggs on tin twigs. The second generation adults in the bivoltine populations lay only diapause eggs; in the trivoltine populations they lay both summer and diapause eggs. The adults of the third generation lay only diapause eggs.The brown mite is found on both the leaves and woody parts of the tree. In orchards with bivoltine populations the proportion of mites on leaves reached a peak of 80% by mid-July, but thereafter gradually decreased to 10% by the end of August. However, in orchards with trivoltine populations the proportion of mites on leaves reached a peak of 80 to 90% by mid-July, remained constant until mid-August, and thereafter decreased to approximately 40% by the end of August.The number of diapause eggs laid by adults of each generation in both the bivoltine and trivoltine populations varies widely. The eggs are deposited on the trunk as well as on the branches, with the heaviest deposition in the central area of the tree. The diapause eggs laid by adults of the first generation are the last to hatch and those laid by the third generation are the first to hatch the following spring.The factors responsible for the differences in the number of generations and in the number of diapause eggs laid are unknown.

scholarly journals ВЪПРОСИ НА БЪЛГАРСКАТА ДИАЛЕКТНА ГЛАГОЛНА МОРФОЛОГИЯ В ИЗСЛЕДВАНИЯТА НА ТРИМА ЕВРОПЕЙСКИ СЛАВИСТИ ОТ ПЪРВАТА ПОЛОВИНА НА XIX ВЕК – ВУК КАРАДЖИЧ, ВИКТОР ГРИГОРОВИЧ, СТЕФАН ВЕРКОВИЧ / ISSUES IN THE VERB MORPHOLOGY OF BULGARIAN DIALECTS IN THE RESEARCH OF THREE EUROPEAN SLAVICISTS FROM THE FIRST HALF OF THE 19TH CENTURY – VUК KARADŽIĆ, VICTOR GRIGOROVICH, STEFAN VERKOVIĆ

2021 ◽  
Vol 68 (68.04) ◽  
pp. 89-100
Author(s):  
MARIA MITSKOVA
Keyword(s):  
19Th Century ◽  
First Generation ◽  
Scientific Interest ◽  
Great Contribution ◽  
Verb Morphology ◽  
Distinctive Features ◽  
Present Tense ◽  
The 19Th Century

As representatives of the first generation of European scholars to observe and describe the Bulgarian vernacular from the 19th century, Vuk Karadžić, Victor Grigorovich and Stefan Verković made a great contribution to the study of the verb morphology of Bulgarian dialects of that time. Their pioneering research mark the emergence of scientific interest to some of the most distinctive features and peculiarities of Bulgarian verbs such as: the loss of the Old Slavonic infinitive, the existence of aorist and past imperfect tense with a variety of dialect forms, the dialectal differences in the present tense conjugations and the large number of phonetic variants of the particle ще used in futuretense formation. Keywords: Bulgarian dialects, morphology of Bulgarian dialects, Bulgarian verbs

Distillery Configurations

2019 ◽  
pp. 47-64
Author(s):  
Karl Raitz
Keyword(s):  
Nineteenth Century ◽  
Labor Force ◽  
First Generation ◽  
Second Generation ◽  
High Capacity ◽  
Third Generation ◽  
Early Nineteenth Century ◽  
Railroad Tracks ◽  
Urban Rail ◽  
Capacity Output

Early-nineteenth-century farmers and millers were often craft distillers, mashing and fermenting grain meal in wooden barrels before distilling the liquid in small copper pot stills. Waterwheels powered the first-generation creek-side mills and distilleries. Wood fueled early steam engines; the use of coal required access to better transportation. Second-generation distilleries, operating from the 1830s to the 1880s, used traditional pot stills,although some adopted new column stills, perfected in Scotland, when they began to mechanize. Old still buildings were often modified to accommodate new machinery. Distillers stored whiskey-filled wooden barrels in stack warehouses to age. Industrialization required a larger labor force. By 1880, businesses in Louisville and other river cities were producing steam engines, boilers, and related equipment. Third-generation distilleries operated from the 1880s to 1920; their high-capacity output required more grain and fuel, mandating locations near railroad tracks or navigable rivers. Complementary industries such as cooperages, metal fabricators, slaughterhouses, and tanneries were attracted to urban, rail-side distilleries.

Failure properties of 352 explanted silicone-gel breast implants

1996 ◽  
Vol 4 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Walter Peters ◽  
Dennis Smith ◽  
Stanley Lugowski
Keyword(s):  
First Generation ◽  
Second Generation ◽  
Survival Curve ◽  
Breast Implants ◽  
Thick Wall ◽  
Thin Wall ◽  
Third Generation ◽  
Silicone Gel ◽  
Failure Properties

There have been three generations of silicone-gel breast implants. First generation implants (thick wall – thick gel with Dacron patches) were made from 1963 to 1972. Second generation implants (thin wall-thin gel) were made from 1972 until the mid 1980s. The introduction of third generation implants (stronger wall, low-bleed) was geographically dependent. In Canada, Dow Corning Silastic II implants were introduced in 1986, and Surgitek SCL implants were introduced in 1988. In the present study, a total of 352 silicone-gel breast implants were removed from 239 patients between 1981 and 1995. Their failure properties were dependent upon their generation (year of manufacture) and, for second generation implants, their duration in situ. Of the 352 implants, 20 were first generation, and all were fully intact. Twenty-eight were third generation implants, and 27 were fully intact. Failure properties of the 302 second generation implants were dependent upon their duration of implantation. A survival curve indicated that these implants began to fail (by leaking or rupturing) after four years in situ. By six years, 40% had failed. After 12 years, 95% had failed. Of the 171 second generation implants removed between 1991 and 1995, 77% had failed. The failure properties were similar for the three main manufacturers: Dow Corning, Heyer-Schulte and Surgitek. The failure rate for second generation implants is much higher than was previously believed. This is particularly significant in view of the current difficulty in diagnosing implant failure.

Brominated β-Alkoxyvinyl Trihalomethyl Ketones as Promising Synthons in Heterocyclic Synthesis

Synthesis ◽  
2020 ◽  
Vol 52 (14) ◽  
pp. 2008-2016
Author(s):  
Mateus Mittersteiner ◽  
Nilo Zanatta ◽  
Helio G. Bonacorso ◽  
Marcos A. P. Martins
Keyword(s):  
First Generation ◽  
Second Generation ◽  
Building Blocks ◽  
Third Generation ◽  
Cycloaddition Reactions ◽  
Heterocyclic Synthesis

5-Bromo- and 5,5-dibromo-1,1,1-trihalo-4-methoxypent-3-en-2-ones (brominated enones) have proven to be attractive building blocks for the construction of heterocyclic and polyheterocyclic compounds bearing a trihalomethyl moiety through interesting cyclocondensation, alkylation, and cycloaddition reactions. This review compiles all of the reactions conducted with these brominated enones since they were first disclosed in 2001.1 Introduction2 Synthesis and Initial Applications3 Synthesis Using First-Generation Intermediates4 Synthesis Using Second-Generation Intermediates5 Synthesis Using Third-Generation Intermediates6 Conclusions

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