Dilip H. Gawad

Some b-Carboline Alkaloids of Ailanthus malabarica DC

From the bark and roots of Ailanthus malabarica DC. we have isolated and characterised eight β-carboline alkaloids of which four are new. Their structures are elucidated by spectroscopic studies.

Attenuol—structure, stereochemistry and synthesis

Abstract A new lignan, attenuol, isolated from Knema attenuata (Wall.) Warb., has been assigned structure (1) on the basis of spectral data. Lignan (1) and the stereoisomer (4) (2-epiattenuol) have been synthesized and the structure assigned to attenuol has been confirmed.

A novel example of a natural 2,5-dihydroxyflavanone from Unona lawii

Abstract 3-Formyl-2,4,6-trihydroxy-5-methyldibenzoylmethane from Unona lawii has been shown to exist in a cyclic hemiketal form whereas 3-formyl-2,6-dihydroxy-4-methoxy-5-methyldibenzoylmethane from the same plant mainly exists in the enolic ring opened form, owing to chelation of both hydroxyl groups. The flavonoid pattern of Unona lawii suggests the biogenetic scheme : flavanone → 2-hydroxyflavanone → flavone. 3-Formyl-2,4,6-trihydroxy-5-methyldibenzoylmethane has been synthesized by Baker-Venkataraman rearrangement of 3-formyl-2,4,6-tri-hydroxy-5-methylacetophenone benzoate.

The structure of radermachol, an unusual pigment from radermachera xylocarpa K. Schum.

The structure of radermachol 1, isolated from the roots of Radermachera xylocarpa K. Schum., has been determined by spectral and X-ray analysis. The fused aromatic ring system of this compound appears to be unique.

Piperaceae alkaloids: Part II1 structure and synthesis of cyclostachine A, A novel alkaloid fromPiper trichostachyon C. DC

A novel alkaloid designated cyclostachine A has been proved to have the structure (II) on the basis of spectral and degradative data. The structure has been confirmed by synthesis, and by X-ray analysis of the derived amine sulphate (III).

Revised structures of pipoxide and pipoxide chlorohydrin

The structures assigned earlier to pipoxide and pipoxide chlorohydrin have been revised on the basis of 360 MHz PMR spectral evidence and decoupling experiments.

The structure of clausantalene, a new sesquiterpene fromClausena indica Oliv.

Es wurde ein neues Sesquiterpen C15H26O2 (Clausantalene) aus den Wurzeln vonClausena indica Oliv. (Rutacene) isoliert. Spektralanalytische und röntgenkristallographische Daten ermittelten ein β-Santalan-Derivat.

Clausindine, a novel cyclopropylcoumarin

From the roots of Clausena indica Oliv., a new coumarin, clausindine, has been isolated and shown to have the structure 6-(2,2-dimethylcyclopropyl)furo[3,2-g][1]benzopyran-7-one (I) mainly on spectroscopic evidence. The structure has been confirmed by a synthesis of dihydroclausindine (II). The furanoquinone, furo[3,2-g][1]benzopyran-4,7,9-trione (XII) has also been isolated from the roots of this plant.

Crystal and molecular structure of crenatine carbonate

The crystal and molecular structure of 1-ethyl-4-methoxy-9H-pyrido[3,4b]indole (crenatine) carbonate C14H14N2O·H2CO3, (MS, m/z 226)MR 288.3, aβ-carboline alkaloid, has been determined from X-ray diffraction data. The compound crystallizes in the space group Pbca with cell parameters:a=11.616(4),b=18.450(8),c=12.992(5)Å,V=2784(2)Å3,Z=8,Dcalc=1.375 g cm−3,λ (MoKα)=0.71069Å,μ(Mo Kα)=0.94 cm−1,F(000)=1216,R/Rw=8.2/10.3% for 1099 reflections. The ring system of theβ-carboline nucleus is planar. The title compound shows a two center hydrogen bond between the indole N-H group and the oxygen atom of a carbonate group. The structure does not display hydrogen bonding betweenβ-carboline groups but rather a bonding network involving the carbonate group.

Chemical constituents ofAtalantia racemosa Wt. and Arn. Structure and synthesis of racemosin, a novel pyranocoumarin

Phytochemical investigation of the aerial parts ofAtalantia racemosa Wt. and Arn. gave the known compounds xanthyletin, xanthotoxin and friedelin. The structure (I) for the new coumarin, racemosin, has been deduced on the basis of UV, IR, NOE, proton and carbon-13 NMR spectral data. The assigned structure for the natural product has been confirmed by synthesis.