C19 quassinoid model studies: Preparation of trans-perhydroindans via a vinylogous Mukaiyama aldol – free-radical cyclization route

2004 ◽  
Vol 82 (2) ◽  
pp. 314-317 ◽  
Author(s):  
Matthew G Donahue ◽  
David J Hart
Keyword(s):  
Free Radical ◽  
Acid Treatment ◽  
Titanium Tetrachloride ◽  
Aldol Reaction ◽  
Radical Cyclization ◽  
Asymmetric Induction ◽  
Model Studies ◽  
Mukaiyama Aldol ◽  
Relationship Of ◽  
The Relationship

Aldehyde 9 was prepared in 5 steps from 3,5-dimethylbenzoic acid. Treatment of 9 with ketene acetals 10 and 19 and titanium tetrachloride gave free-radical cyclization substrates 11 and 20 in 67% and 51% yields, respectively. Tri-n-butylstannane-mediated cyclization of 11 and 20 gave trans-perhydroindans 14 and 21 in 60% and 63% yields, respectively. The relationship of these studies to an approach to C19 quassinoids is discussed.Key words: vinylogous Mukaiyama aldol reaction, free-radical cyclization, trans-perhydroindans, C19 quassinoids, 1,2-asymmetric induction.

The Relationship of Free Radical Scavenging and Total Phenolic and Flavonoid Contents of Garcinia lasoar PAM

2020 ◽  
Vol 53 (12) ◽  
pp. 1151-1157 ◽  
Author(s):  
Healthy Kainama ◽  
Sri Fatmawati ◽  
Mardi Santoso ◽  
Pamella Mercy Papilaya ◽  
Taslim Ersam
Keyword(s):  
Free Radical ◽  
Radical Scavenging ◽  
Free Radical Scavenging ◽  
Total Phenolic ◽  
Relationship Of ◽  
The Relationship ◽  
Phenolic And Flavonoid

scholarly journals Design and Synthesis of a Chiral Halogen-Bond Donor with a Sp3-Hybridized Carbon–Iodine Moiety in a Chiral Fluorobissulfonyl Scaffold

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4539
Author(s):  
Hiroto Uno ◽  
Kohei Matsuzaki ◽  
Motoo Shiro ◽  
Norio Shibata
Keyword(s):  
Halogen Bond ◽  
Aldol Reaction ◽  
Asymmetric Induction ◽  
Nmr Titration ◽  
Titration Experiment ◽  
Mukaiyama Aldol Reaction ◽  
Design And Synthesis ◽  
Mukaiyama Aldol

The first example of a chiral halogen-bond donor with a sp3-hybridized carbon–iodine moiety in a fluorobissulfonyl scaffold is described. The binaphthyl backbone was designed as a chiral source and the chiral halogen-bond donor (R)-1 was synthesized from (R)-1,1′-binaphthol in 11 steps. An NMR titration experiment demonstrated that (R)-1 worked as a halogen-bond donor. The Mukaiyama aldol reaction and quinoline reduction were examined using (R)-1 as a catalyst to evaluate the asymmetric induction.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

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