Industrial Synthesis of Maxacalcitol, the Antihyperparathyroidism and Antipsoriatic Vitamin D3 Analogue Exhibiting Low Calcemic Activity

Chemical synthesis of marine saponins

Covering: 1989-2017 Saponins are characteristic metabolites of starfish and sea cucumbers, and occasionally are also found in sponges, soft coral, and small fish. These steroid or triterpenoid glycosides often show remarkable biological and pharmacological activities, such as antifungal, antifouling, shark repellent, antitumor and anti-inflammatory activities. Over one thousand marine saponins have been characterized; the majority of them can be categorized into three major structural types, i.e., asterosaponins, polyhydroxysteroid glycosides, and holostane glycosides. Thus far, only 12 marine saponins have been synthesized; those representing the major types were successfully synthesized recently. The syntheses involve preparation of the aglycones from the terrestrial steroid or triterpene materials, installation of the carbohydrate units, and manipulation of the protecting groups. Herein, we provide a comprehensive review on these syntheses.

Effects of 2-substitution on 14-epi-19-nortachysterol-mediated biological events: based on synthesis and X-ray co-crystallographic analysis with the human vitamin D receptor

Both 2α- and 2β-hydroxypropyl substituted 14-epi-1α,25-dihydroxy-19-nortachysterols were synthesized to study the human vitamin D receptor (hVDR) binding affinity, binding configurations, and interactions with amino acid residues in the ligand binding domain of hVDR by X-ray co-crystallographic analysis. In conjunction with our previous results on 14-epi-19-nortachysterol, 2-methylidene-, 2α-methyl-, 2β-methyl, and 2α-hydroxypropoxy-14-epi-19-nortachysterol, we propose a variety of effects of substitution at the C2 position in the 14-epi-19-nortachysterol skeleton on biological activities.

First synthesis of 22-oxa-chenodeoxycholic acid analogue

In this study, we report the first synthesis of 22-oxa-chenodeoxycholic acid analogue via androstenedione and progesterone, in 11 and 8 steps with overall yields of 6.4% and 12.7%, respectively. We anticipate this will help to facilitate the development of new drugs.

Stereoselective reduction of C-20 ketone of vitamin D CD-ring and a new synthetic approach to maxacalcitol

Stereoselective reduction of C-20 ketone of vitamin D CD-ring precursor using Corey's CBS reagents, (R)-(+)-2-methyl-CBS-oxazaborolidine and (S)-(-)-2-methyl-CBS-oxazaborolidine, led to the (20S)-alcohol 5 and (20R)-epimer 4 in approximately 17:1 selectivity. A new synthetic approach to the 22-oxa-25-hydroxy Grundmann's ketone 11 was developed through the Williamson etherification of (20S)-alcohol 5 with 1-bromomethyl-2,2-dimethyloxirane, followed by regioselective reductive epoxide ring opening with LiAlH4, the removal of the silyl protecting group by TBAF, and the environmentally benign TEMPO-mediated oxidation using inexpensive Oxone as a co-oxidizing agent. The preparation of drug maxacalcitol was achieved on gram scale by the convergent Lythgoe coupling via Wittig-Horner reaction of the A-ring phosphine oxide synthon with the CD-ring fragment.

Total synthesis of starfish saponin goniopectenoside B

Star quality: Goniopectenoside B, a minor asterosaponin from starfish Goniopecten demonstrans with antifouling activity, has been synthesized in a convergent 21 steps and in 4.3 % overall yield starting from adrenosterone. This represents the first synthesis of a complex asterosaponin, which are ubiquitous and characteristic in starfish as defense chemicals (see figure).

Design and evaluation of new antipsoriatic antedrug candidates having 16-en-22-oxa-vitamin D3 structures

Design, synthesis, and in vitro and in vivo evaluation of a series of antipsoriatic antedrugs having 16-en-22-oxa-vitamin D3 are described. Among the seven compounds examined, two are promising: ester 5c and amide 5f, both of which exhibit greater potent antiproliferation activity with lessened calcemic activity than the presently prescribed maxacalcitol (2).

Novel vitamin D3 antipsoriatic antedrugs: 16-En-22-oxa-1α,25-(OH)2D3 analogs

A series of 16-en-22-oxa-derivatives of vitamin D3 based on the structure of maxacalcitol (2) were prepared. Maxacalcitol is currently used topically for the treatment of psoriasis and is recognized as the most successful antedrug of natural vitamin D(3) because it retains the original antiproliferative activity of calcitriol without increased calcemic activity. We introduced 16-olefinic functionality to accelerate the oxidative metabolism of the drug in liver, presumed to be essential for the reduction of calcemic activity, and modified the side-chain moiety by placing the 22-oxygen on the more labile allylic carbon center. Novel 22-oxa analogs (7a-i), carrying either the 24-alkynyl bond or 24-hydroxy functionality in addition to the 16-double bond were synthesized and their pharmacokinetics were evaluated.