For example, the starting β amide, β acid ester, or β thiolcarbonic acid ester can first be reacted with the silylating agent and then reacted with the cyclizing agent, or the starting compound can be added to a mixture of {TAIL ~ the silylating agent} and {HEAD ~ the cyclizing agent} 
For example , the starting β amide , β acid ester , or β thiolcarbonic acid ester can first be reacted with the silylating agent and then reacted with the cyclizing agent , or the starting compound can be added to a mixture of { TAIL ~ the silylating agent } and { HEAD ~ the cyclizing agent }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD