Gabriel Tojo

Preparation of phenanthrenes by photocyclization of stilbenes containing a tosyl group on the central double bond. A versatile approach to the synthesis of phenanthrenes and phenanthrenoids.

We have developed a useful modification of the classical preparation of phenanthrenes by UV irradiation of stilbenes in the presence of an oxidant. This modification involves the irradiation, in the presence of base, of stilbenes possessing a sulfonyl group linked to the central double bond. We have proved that this protocol can be successfully applied for the synthesis of diverse phenanthrenes and phenanthrenoids.

Isolation and identification of vitamin D3, 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and 1,24,25-trihydroxyvitamin D3 in Solanum malacoxylon incubated with ruminal fluid

It has been shown that Solanum malacoxylon contains 1 alpha,25-dihydroxyvitamin D3-glycoside. The presence of vitamin D3 and 25-hydroxyvitamin D3 has also been suggested. In the present study vitamin D3 and three of its metabolites, including 1 alpha,25-dihydroxyvitamin D3, were detected in plant leaf extracts preincubated with ruminal fluid (SMRF). Extraction of SMRF with non-polar organic solvents and purification of the lipid extract by TLC followed by HPLC yielded nine ultraviolet-absorbing (264 nm) peaks. Four of them comigrated on a Zorbax-Sil HPLC column with synthetic standards of vitamin D3, 25-hydroxyvitamin D3, 1 alpha,25-dihydroxyvitamin D3 and 1,24R,25-trihydroxyvitamin D3, respectively. These compounds were unequivocally identified by means of mass spectrometry. The results confirm that Solanum malacoxylon contains, in addition to 1 alpha,25-dihydroxyvitamin D3, vitamin D3, 25-hydroxyvitamin D3 and possibly other as yet unidentified derivatives. As 1,24,25-trihydroxyvitamin D3 is absent in plant extracts not incubated with ruminal fluid, the data also indicate that rumen microbes may convert 1 alpha,25-dihydroxyvitamin D3 into 1,24,25-trihydroxyvitamin D3.

New One-Pot Synthesis of Alkyl Nitrates from Alcohols

Abstract Treatment of alcohols with Ph3P-I2-invidazole followed by “in situ” reaction of the generated iodides with AgNO3 allows the mild conversion of alcohols into alkyl nitrates. Unlike previous procedures, this one requires no electrophilic nitrating conditions.

Phenol Nitration from A 2-(Nitrooxy)Ethyl Side Chain

Abstract A novel nitration of phenols is described on 2-(3-hydroxy-4-methoxyphenyl)ethyl nitrate (2), which is synthesized by three alternative routes.

Photocyclization of tosylstilbenes as a key reaction in the preparation of an analogue of the antitumor agent CC-1065.

A photocyclization of tosylstilbenes in the presence of base is used as a key reaction in the synthesis of the CC-1065 analogue 5.

Oxidation of Alcohols to Carboxylic Acids via Isolated Aldehydes

Not surprisingly, the oxidation of primary alcohols to acids involves more rigorous experimental conditions than the oxidation to aldehydes, which possess a lower oxidation state than acids. Therefore, the milder oxidizing conditions needed for obtention of aldehydes offer better prospects for selective oxidations, particularly in sensitive and complex molecules possessing oxidation-sensitive moieties other than primary alcohols. Consequently, a two-step oxidation of primary alcohols to acids, via an intermediate aldehyde that is isolated, is a valuable synthetic alternative in some difficult substrates. The transformation of aldehydes into acids usually does not interfere with other sensitive functional groups because aldehydes are normally very easily oxidized under quite mild conditions. In fact, an inspection of the modern literature shows that, in a proportion as high as ca. 40%, the conversion of alcohols to acids is carried out using two separate synthetic operations, with isolation of the intermediate aldehydes. This highlights the fact that the direct oxidation of primary alcohols to acids is an immature technique in need of more selective reagents. A listing of instances in which a two-step transformation of primary alcohols into acids is preferred over a direct one-step oxidation is shown below.

STUDIES ON THE SYNTHESIS OF THE ANTITUMOR AGENT CC-1065 : PREPARATION OF ISOPROPYL 6-HYDROXY-7-METHOXY-4-(2-NITROOXYETHYL)INDOLE-2-CARBOXYLATE

Abstract The title indolecarboxylate (1) is synthesized as a potential intermediate for the preparation of the central and right parts of CC-1065 (2).

Chapter 3 Phenanthrene Alkaloids

Publisher Summary This chapter discusses all natural phenanthrene alkaloids, and includes many references to unnatural phenanthrenes. The phenanthrene alkaloids are derivatives of 1-(2-aminoethyl) phenanthrene, which have close relationship with aporphine alkaloids. Phenanthrene alkaloids with a 2-(methylamino) ethyl side chain are 6,6a-secoaporphines, whereas those with a 2-(dimethylamino)ethyl chain are referred as methines of the corresponding aporphine. Phenanthrene alkaloids are found in the following families of the Angiospermae: Annonaceae, Aristolochiae, Berberidaceae, Fumariaceae, Hermandiaceae, Menispermaceae, Monimiaceae, and Ranunculaceae. The mass spectra of phenanthrene alkaloids are very informative regarding the nature of the side chains. Most phenanthrene alkaloids are easily synthesized by degradation of the corresponding aporphines. Many phenanthrenes are first prepared as aporphine derivatives for characterization or in the course of structural studies, and are later found in nature.