The present invention is directed to compounds of formula which are M1 receptor positive allosteric modulators and that are useful in the treatment of diseases in which the M1 receptor is involved, such as Alzheimer’s disease, schizophrenia, pain or sleep disorders. In an exemplary synthetic method, a bio-derived flame retardant block copolymer is prepared by a ring opening polymerization of a biobased cyclic ester and a phosphorus-containing polymer. The dividers may be angled on the gondola.