Ramón Alvarez-Manzaneda

Achilleol A: A new monocyclic triterpene skeleton from Achillea odorata L.

A new triterpene 1a from Achillea odorata L. has been isolated, and its structure established on the basis of its spectroscopic properties as well as those of its acetylderivative 1b. 1a shows the first example of monocyclic triterpene skeleton, biosynthetized in the first step of cyclization of squalene oxyde.

Bioactive sesquiterpenes from Santolina rosmarinifolia subsp. Canescens. A conformational analysis of the germacrane ring

The hexane extract of aerial parts of Santolina rosmarinifolia subsp. canescens afforded eight new sesquiterpenes in addition to known compounds. Their structures were determined by spectroscopic methods and chemical transformations. The conformational analysis of the germacrane constituents was carried out by spectroscopic methods, including NMR at varying temperature and by molecular mechanics calculations. The antifeedant, antibacterial and antitumoral activity of selected compounds has been tested.

A Very Efficient Route toward the 4a-Methyltetrahydrofluorene Skeleton: Short Synthesis of (±)-Dichroanone and (±)-Taiwaniaquinone H

A very expedient and efficient new route toward taiwaniaquinoids, bearing the 4a-methyltetrahydrofluorene skeleton, is reported. Key steps are the intramolecular Friedel-Crafts alkylation of an aryldiene and the degradative oxidation of a methylenedioxy group; the latter process could also be utilized for building the 2-hydroxy-1,4-benzoquinone unit, which is frequently found in natural products. Utilizing this new methodology, (+/-)-dichroanone (7) (three steps, 77% overall yield) and (+/-)-taiwaniaquinone H (6) (four steps, 70% overall yield) have been synthesized from commercial alpha- (11a) or beta-cyclocitral (11b).

General Access to Taiwaniaquinoids Based on a Hypothetical Abietane C7–C8 Cleavage Biogenetic Pathway

A new strategy for synthesizing taiwaniaquinoids, a group of terpenoids with an unusual rearranged 5(6→7) or 6-nor-5(6→7)abeo-abietane skeleton, which exhibit promising biological activities, is reported. The procedure, based on the cleavage of the C7-C8 double bond of abietane diterpenes, is the only one yet reported for synthesizing C(20) taiwaniaquinoids bearing a carbon function on the cyclopentane B ring; it is also applicable to the synthesis of the wide variety of existing taiwaniaquinoids. Utilizing this, (-)-taiwaniaquinone A, F, G, and H, (-)-taiwaniaquinol B, and (-)-dichroanone have been synthesized from (+)-abietic acid. The versatility of this strategy allows us to propose the abietane C7-C8 cleavage as a possible biosynthetic pathway to this type of rearranged diterpenes; this proposal seems to be supported by phytochemical evidence.

Sesquiterpenes from Santolina chamaecyparissus subsp. squarrosa

Abstract Four new sesquiterpenes, (E)-6β-acetoxy-7αH-germacra-4,10(14)diene-1α,2β-diol (1), (4E,9Z)-6β-acetoxy-7-αH- germacra-4,9-diene-1α,2β-diol (2), (E)-6β-acetoxy-7αH-germacra-1(10),4-diene-2β-ol (3) and 6β-acetoxy-5βH,7αH,10βMe-eudesm-4(15)-ene- 1α,2β-dol (4), were identified in the ether extract from the aerial parts of Santolina chamaecyparissus subsp. squarrosa. Their structures and preferred conformation in solution were determined by spectroscopic methods and molecular mechanics calculations.

The first route toward oxygenated monocarbocyclic terpenoids: synthesis of elegansidiol, a new sesquiterpene from Santolina elegans

This paper describes the isolation of elegansidiol (1), a new monocyclic sesquiterpenic alcohol, together with the known monocyclic triterpene achilleol A (2), both from Santolina elegans. The structure of 1 was confirmed by synthesis starting from 6,7-epoxygeranyl acetate (6), constituting the first route towards this type of compound.

Microbial allylic hydroxylation of some octalone derivatives

Abstract 7β-Hydroxy octalone derivatives are obtained efficiently by allylic hydroxylation of 4 and 6 with Rhizopus arrhizus .

Bisabolene derivatives and other constituents fromAchillea odorata

Abstract From a hexane extract of the aerial parts of Achillea odorata , two nerolidol derivatives, (6 E )-5,9-diacetoxynerolidol and (6 E )-9-acetoxy-5-hydroxynerolidol, six bisabolene derivatives, 7,10-dihydroxy-bisabol-2,11-diene, 7,11-dihydroxy-bisabol-2,9 E -diene, 1,10-diacetoxybisabol-2,11-diene, 7-hydroxy-11-hydroperoxybisabol-2,9 E -diene, 7-hydroxy-10-hydroperoxybisabol-2,11-diene and (−)-α-bisabolol, as well as two flavones, 3,6,7,4′-tetramethoxy-5-hydroxyflavone and 3,6,7,3′,4′-pentamethoxy-5-hydroxyflavone, have been isolated. Structures of the first three new terpenoids were established from their spectroscopic properties and by the use of some chemical correlations.

Microbial hydroxylations of further octalin derivatives

Abstract The allylic hydroxylation of octalin derivatives with Rhizopus arrhizus proceeds with high to excellent yields, even in the presence of substituents such as acetate, phosphate, free ketone or dioxolane, but not a benzyl group. One of the Me groups of a t-Bu ether can be hydroxylated.

NIS–PPh3: A Selective Reagent for the Spiroannulation of o-Allyl Phenols. Total Synthesis of Corallidictyal D

Treatment of o-allyl phenols with catalytic NIS-PPh3 affords the corresponding spirodihydrobenzofuran derivatives in high yield with high regio- and total stereoselectivity under mild conditions. These results were utilized to achieve the first total synthesis of the protein kinase C inhibitor corallidictyal D starting from α-ionone.