Steroid acetate

Steroid molecules can be constructed by applying the benzocyclobutene-o-xylylene method. When the compound (329) was heated in o-dichlorobenzene at 180 °C for 14 hours, the compound (330) was isolated, which could be converted by a number of steps to the steroid acetate (331) u4). 

Nitrophenyl)ethylene glycol was used to protect simple aldehydes and ketones, as well as some steroids. Acetals were prepared under acid catalysis, leading, in the case of chiral carbonyl compounds to diaste-reoisomers. The photochemical removal of the protecting group was in several instances complicated by the instability of some carbonyl derivatives to irradiation at 350 nm otherwise, yields were in the range of 83-90% (see Scheme 19). 

The preceding loss of acetic acid is so facile in steroidal acetates that they frequently show no detectable molecular ion peak. Steroidal systems also seem unusual in that they often display significant molecular ions as alcohols, even when the corresponding acetates do not. 

H. C. Van den Berg, Quantitative determination of steroid acetates in pharmaceutical preparations by HPLC, J. Assoc. Off. Anal. Chem., 63 1184(1980). 

Fluocinolone acetonide is a steroid acetal used to treat skin conditions such as eczema and psoriasis. The acetal group decreases the water solubility of the parent steroid, enhancing its potency and allowing for a longer duration of action. 

Jones et al. [ 1 ] have also examined three steroid acetates in which ring I is fully aromatic. As is to be expected, this results in a shift of the C—O stretching frequency, and the strongest band in this re on is now found near 1205 cm . The position of the C—O absorption in these, and in saturated steroid acetates, is inversely tied to that of the carbonyl absorption, and a simple linear relation connects the two [65]. 

Many procedures have also been developed for acid-sensitive compounds. Use of either adipic or Oxalic Acid gives good yields of sensitive steroid A -3-ethylene acetals. Selenium(IV) Oxide has also been used effectively for steroid acetalization (eq 6)P... 

N,N-DimethylformamidelDimethyl Sulfate is another mild acetalization catalyst. Metal catalysts, such as Rh complexes and Palladium on Carbon have also been used effectively (eqs 9 and 10). Ion-exchange resins offer significant advantages for the preparation of sensitive steroid acetals (eq 11). An especially convenient method involves running a solution of the ketone and ethylene glycol through a column of Amberlyst. Zeolites have also been used to prepare acetals. ... 

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