the forskolin analogs utilized in the method and compositions of the invention may be prepared by standard procedures . a convenient starting material for preparing these compounds in 7β - acetoxy - 8 , 13 - epoxy - 1 , α , 6β , 9α - trihydroxylabd - 14 - en - 11 - one , forskolin , [ j . c . s . perkin i , 767 ( 1982 )]. those skilled in the art will recognize that in order to carry out a particular desired synthetic conversion it may be necessary to first protect other reactive sites which may be present in a molecule . such protection is preferably accomplished by first forming a derivative at the site to be protected which derivative may be readily re - converted to the original functionality , if desired , after the particular synthetic conversion has been carried out . examples of such protective conversions are esterification of alcohols and ketalization of ketones . other such conversions will suggest themselves to those skilled in the art . because such techniques are recognized as within the skill of the art , they are not included in the following description of the preparation of the compounds utilized in the method of the invention . compounds wherein r 1 is ═ o may be prepared by oxidizing a corresponding compound wherein r 1 is oh . compounds wherein r 1 is or 11 may be prepared by acylation of a compound wherein r 1 is oh . compounds wherein r 1 is h may be prepared by reduction of a compound wherein r 1 is ═ o . compounds having r 2 substituents as described herein may be prepared substantially as described hereinabove for a corresponding r 1 substituent . compounds wherein r 1 and r 2 together form ## str12 ## may be prepared by reacting a corresponding compound wherein r 1 = r 2 = oh with an aldehyde or ketone . such reactions are generally carried out using conditions whereby the reaction - produced water may be continuously removed . compounds having the additional bond , a , may be produced for example by dehydration of a suitable compound wherein r 1 and / or r 2 are hydroxy . compounds wherein r 3 is cho may be prepared from the starting compound ( which has a vinyl group at this position ) by ozonolysis . compounds wherein r 3 is ch 2 oh or co 2 r 15 may be prepared respectively by reducing or oxidizing the corresponding aldehyde . the carboxylic acid so produced ( r 15 = h ), thereafter may be esterified if desired . compounds wherein r 3 is -- ch ═ cr 16 r 17 may be prepared by treating a compound wherein r 3 is cho with a wittig reagent , φ 3 p ═ cr 16 r 17 . certain of the substituents , r 16 and r 17 may be modified or interconverted subsequent to the wittig reaction , when desired . compounds wherein r 3 is -- c . tbd . c -- r 18 may be prepared by treating a compound wherein r 3 is cho with a reagent φ 3 p + chbrr 18 to produce a bromine containing intermediate which may be dehydrobrominated to produce the desired product . compounds wherein r 3 is c . tbd . ch may be prepared by the addition of bromine to a corresponding compound wherein r 3 is -- ch ═ ch 2 followed by didehydrobromination . compounds wherein r 3 is -- choh -- c . tbd . c -- r 19 may be prepared from a compound wherein r 3 is cho by treatment with a reagent , mc . tbd . c -- r 19 , wherein m is a suitable metal such as lithium . compounds wherein r 3 is -- ch ═ c ═ chr 19 may be prepared from a corresponding compound wherein r 3 is -- choh -- c . tbd . c -- r 19 by first esterifying the hydroxyl group and treating the so obtained ester with aluminum chloride . compounds wherein r 3 is -- ch ═ n -- or 19 may be prepared from a compound wherein r 3 is cho by treatment with a reagent of the formula h 2 n -- or 19 . compounds wherein r 3 is ## str13 ## may be prepared from a compound wherein r 3 is -- ch ═ cr 16 r 19 by treatment with a per acid such as m - chloroperbenzoic acid to produce compounds wherein z is oxygen , these compounds may be converted to corresponding compounds wherein z is sulfur by treatment with potassium isothiocyanate . compounds wherein r 3 is -- ch ( zr 20 ) 2 may be prepared from a compound wherein r 3 is cho by treatment with an alcohol or thiol using standard procedures . compounds wherein r 3 is ## str14 ## may be prepared by the addition of a dihalocarbene to a compound wherein r 3 is -- ch ═ ch 2 or by the addition of a methylene carbene to a compound wherein r 3 is -- ch ═ cab . compounds wherein r 3 is -- ch ═ n -- nde may be prepared by treating a compound wherein r 3 is cho with a compound having the formula h 2 n - nde using standard procedures . compounds wherein r 4 is hydrogen may be prepared , for example , by first forming an internal 1 , 9 - carbonate or thiocarbonate ester utilizing a starting material wherein r 4 = r 5 = oh . convenient reagents for performing these conversions are carbonyl diimidazole or thiocarbonyl diimidazole , respectively . the so produced esters upon treatment with zinc in acetic acid produce the compound wherein r 4 is hydrogen and r 5 is hydroxy . the compounds of this invention wherein x is h / oh may be prepared by a suitable reduction of a compound wherein x is ═ o . when utilized herein the following terms will have the indicated meanings unless otherwise specified : alkyl -- straight and branched carbon chains having from 1 to 6 carbon atoms ; alkoxy and alkylthio -- comprised of straight and branched carbon chains having from 1 to 6 carbon atoms which are singly bonded respectively to an oxygen or a sulfur atom ; carboxylic acyl -- the acyl portion derived from a straight or branched chain alkanoic acid having from 1 to 6 carbon atoms ; alkenyl -- straight or branched carbon chains comprising one double bond and having from 2 to 6 carbon atoms ; alkynyl -- straight and branched carbon chains comprising one triple bond and having from 2 to 6 carbon atoms . the following numbering system is utilized herein for the forskolin skeleton unless specified othewise : ## str15 ## a dashed line ( ) indicates that the substituent is projected below the plane of the paper and is denoted as α ; a heavy line () indicates that the substituent is projected above the plane of the paper and is denoted as β . the active compounds utilized in this invention may exist as solvates , for example as hydrates . certain compounds utilized in the invention may exist as optical and / or geometric isomers . for example , substituents and positions 6 , 7 and 11 of the forskolin skeleton as well as certain r 3 substituents may exist in isometric forms . the invention contemplates all isomers both in pure form and in admixture . examples of preferred beta adrenergic agonists are isoproterenol ( 3 , 4 - dihydroxy - α -[( isopropylamino )- methyl ] benzyl alcohol ), terbutaline ( 1 -[( 3 , 5 - dihydroxy - phenyl )- 2 ]-( t - butylamino ) ethanol ), metaproterenol ( 1 -( 3 , 5 - dihydroxyphenyl )- 2 - isopropylaminoethanol ), albuterol ( 2 -( t - butylamino )- 1 -( 4 - hydroxy - 3 - hydroxymethylphenyl )- ethanol and the like . for purposes of the invention , the term &# 34 ; subthreshold bronchodilating effective amount &# 34 ; means a dosage of the indicated material which is insufficient to elicit clinically effective ( observable ) bronchodilation in a mammal , when such dosage is administered by a particular route . for example , albuterol is a clinically effective bronchodilator when administered by oral inhalation at a dosage of 180 micrograms ( mcg ). thus , for purposes of the invention , the subthreshold bronchodilating effective amount of albuterol when administered by oral inhalation would be an amount less than 180 mcg . those skilled in the art will appreciate that the &# 34 ; subthreshold bronchodilating effective amount &# 34 ; will consist of a range of doses , and that there will be a lower limit to said amount below which , the present invention will not operate . for purposes of this invention , this lower limit or minimum dosage may be considered to be about 5 % of the effective dose of the particular component . the subthreshold bronchodilating effective amount whether for forskolin , a particular forskolin derivative or for a particular beta adrenergic agonist will be variable and will depend on , inter alia , the potency of the particular material , the particular route of administration , the combination being administered and the age , size and condition of the patient being treated as well as on the severity of the disease state . the choice of the optimum subthreshold . bronchodilating effective amount for each component is therefore best left to the trained clinician attending a particular patient . further , administration is best begun at dosage levels which are considered less than optimum and then adjusted as dictated by the needs of the particular patient . the following subthreshold bronchodilating effective amounts of forskolin and albuterol ( both exemplary constituent medicaments of the invention ) are given merely for purposes of guiding the clinician in instituting therapy . the inhalation route for both medicaments has been chosen as being exemplary of a clinically useful route of administration : the forskolin or forskolin derivative component of the invention may be administered either separately from or in combination with the beta adrenergic agonist component of the invention . any convenient , therapeutically useful route of administration may be utilized . further , the components may be administered by different routes and at different times for purposes of efficacy and / or convenience . thus , for example , a combined dosage form suitable for administration by the inhalation route which comprises 200 - 2000 mcg forskolin and 5 - 150 mcg albuterol may be administered four times a day or as required . alternately , the beta adrenergic agonist component may be administered separately by inhalation , oral or by the intravenous route and the forskolin or forskolin derivative may be administered by the inhalation route . this latter regimen allows additional flexibility in administering the components since each component may be administered on an independent time scale in order to provide an optimal effect . the components of the invention can be administered in conventional oral dosage forms such as capsules , tablets , pills , powders , suspensions or solutions prepared with conventional pharmaceutically acceptable excipients and additives , using conventional techniques . parenteral preparations , i . e . sterile solutions or suspensions are also made by conventional means . inhalation administration can be in the form of a nasal or oral spray . insufflation is also contemplated . topical dosage forms can be creams , ointments , lotions and the like . other dosage forms which can be utilized are transdermal devices and suppositories . the following test procedure was utilized to assess the usefulness of subthreshold bronchodilating effective amounts of the components of the invention for inhibiting bronchospasm . male hartley guinea pigs were killed with a blow to the head and the trachea removed and cut into segments . each segment was suspended in an organ bath containing 10 ml of warmed ( 32 ° c .) krebs - henseleit - bi - carbonate buffer gassed with 95 % o 2 , 5 % co 2 . the tissue was allowed to equilibrate for 30 minutes to a 1 - 2 gram tension , recorded isometrically with a grass tf . 03 pressure transducer . addition of forskolin or albuterol to the tissue caused a dose related relaxation with ec 50 values of 2 . 6 × 10 - 7 and 7 . 6 × 10 - 8 m , respectively . at a subthreshold concentration of 1 × 10 - 8 m , forskolin alone produced 6 % relaxation , while albuterol alone produced 18 % relaxation . a combination of 1 × 10 - 8 m forskolin with 1 × 10 - 8 m albuterol produced 79 % relaxation .
a method for producing bronchodilation in a mammal is disclosed . composition for use in said method are also described .