Ch. Bheemasankara Rao

Diterpenes from the brown alga Dictyota divaricata of the indian ocean

The brown alga Dictyota divaricata from the coasts of the Andaman and Nicobar Islands in the Indian Ocean yielded one known and 11 new diterpenes of which four are dolabellanes, six are dolastanes, and one is a novel aromatic isodolastane. The structures of (1R*,3E,6S*,7E,11S*)-6- hydroxydolabella-3,7,12-triene, (1S*,3S*,4R*, 6S*,7E,11S*)-3,4-epoxy-6- hydroxydolabella-7,12-diene, (1R*,3Z,7E,11S*,12S*)-12-hydroxydolabella-3,7- dien-2-one, (1R*,3Z,7Z,11S*,12S*)-12-hydroxydolabella-3,8-dien-2-one, (1S*,11S*)-3,4;7,8-diepoxy-18-hydroxydolabella-12-ene, (5S*,8S*,9S*, 12R*,13R*,14R*)-9,13-dihydroxydolasta-1,3-diene, (5S*,8S*,9S*, 12R*,13R*,14R*)-13-acetoxy-9-hydroxydolasta-1,3-diene, (5R*,8S*,9 S*,12R*,14S*)-9-hydroxydolasta-1,3-dien-13-one, (5R*,8S*,9S*,12R*, 13S*,14S*)-9,13-dihydroxydolasta-1,3-diene, and (8S*,9S*,12R *)-9-hydroxyisodolasta-1,3,5(14)-trien-13-one were established by interpretation of spectral data and chemical interconversions. Two stereoisomers of (8S*,9S*,12S*)-9-hydroxydolasta-1,3-diene were isolated but their stereochemistries could not be completely elicidated.

Diterpenes from the brown alga Dictyota bartayresiana

The brown alga Dictyota bartayresiana collected in the Gulf of Mannar of the Indian Ocean yielded diterpenes consisting of one known dolastane, five known dolabellanes and five new compounds that were characterized as (1S*,3E,5R*, 7E,11S*,12S*)-5-acetoxy-12-hydroxydolabella-3,7-dien-9-one, (1S*,3E,5R*,7Z,11S*, 12S*)-5-acetoxy-12-hydroxydolabella-3,7-dien-9-one, (1R*,3Z,7E,11S*)-9-acetoxydolabella-3,7,12-trien-16-al, (5R*,8S*,9S*,12S*,14S*)-9-hydroxydolasta-1,3-dien-6-one (1R*,4S*,5R*,8S*,9S,12S*, 14R*)-trihydroxydolasta-2-en-6-one, by interpretation of high resolution spectral data and chemical interconversions.

Divarinone, a novel diterpene from the brown algaDictyota divaricata of the indian ocean

An Indian Ocean specimen ofDictyota divaricata contains divarinone (1), which is the first example of a new class of diterpene having a novel tricarbocyclic skeleton.An Indian Ocean specimen ofDictyota divaricata contains divarinone, which is the first example of a new class of tricyclic diterpene

Chemical examination of Embelia ribes—II : Analogues of vilangin and anhydrovilangin

Abstract By the condensation of embelin (I) with various aldehydes, analogues of vilangin (II) and anhydrovilangin (III) have been synthesized and their properties recorded.

Alcyonacean Metabolites VII – Chemical Constituents of Lobophytum denticulatum and Lobophytum strictum of the Indian Ocean

Abstract A rare cembranoid diterpene, (7E,11E,1R,2S,3R,4R,14S)-14-acetoxy-3,4-epoxycembra-7,11,15-triene-17,2-olide (1), was isolated from Lobophytum denticulatum and a new polyhydroxysterol, 7α-hydroxyandamansterol (9) has been identified as peracetyl derivative from Lobophytum strictum. Several known polyhydroxysterols have also been isolated from these organisms. 1 exhibited moderate antibacterial activity.

The chemistry of flavans and related compounds—I

Abstract Starting from 7-hydroxy-6-ethylflavan (I) and its formyl derivative (IV), 6-ethyl-(7,8,2′,3′)-chromonoflavan (III) of the draconal type and α-pyronoflavans have been synthesized.

Chemical constituents of Pseudopterogorgia species of the Indian ocean.

Abstract A new ceramide, (2S,3R,4E)-1,3-dihydroxy-2-[(hexadecanoyl)amino]-nonadeca-4-ene (1), cholest-5-en-3β,7β,19-triol (2), identified as its, peracetyl derivative (3), and batyl alcohol (4) were isolated from Pseudopterogorgia species. 1 exhibited antibacterial activity against Gram-positive and Gram-negative bacteria.

Analytical application of embelin

SummaryEmbelin is reported as a new reagent for gravimetric estimation of (1) uranium in pure solutions at pH 6.0–6.5 and (2) thorium in acid solutions of 0.4 N HCl. In both cases, the precipitates were ignited and weighed as U3O8 and ThO2. The separation of thorium from large excess of uranium and rare earths could also be effected employing this reagent. In addition, Cu, Cd, Ca, Ba, Sr, Al, Be, Mn, Mg and Zn do not interfere.

Analytical application of embelin: Part IV Estimation of alkaline earths and magnesium

SummaryEmbelin is employed as a reagent for the gravimetric individual estimation of alkaline earth metals and magnesium.ZusammenfassungZur gravimetrischen Einzelbestimmung von Magnesium und den Erdalkalien wird Embelin als Reagens empfohlen.